सी ++ में मोनाड्स और डू-नोटेशन

जैसा कि आप जानते हैं, हास्केल में मठ हैं, लेकिन वे सी ++ में नहीं हैं। लेकिन कुछ भी नहीं सी + + में मठों के कार्यान्वयन को रोकता है। आइए देखें कि क्या हमारे पास उनके कार्यान्वयन के लिए आवश्यक सब कुछ है:

• किसी फ़ंक्शन को किसी अन्य फ़ंक्शन के तर्क के रूप में पास करना है।
• लैम्ब्डा फ़ंक्शन - हां, C ++ 11 में जोड़ा गया। मुझे यकीन नहीं है कि वे भिक्षुओं के कार्यान्वयन के लिए आवश्यक हैं, लेकिन उनके साथ, निश्चित रूप से, आसान है।
• टाइप कक्षाएं - नहीं। सी ++ में वे अपने एनालॉग - अवधारणाओं को जोड़ना चाहते थे, लेकिन अभी तक इसे नहीं जोड़ा है। लेकिन मठों के कार्यान्वयन के लिए, उन्हें ज़रूरत नहीं है, आप बस विशिष्ट मठों के लिए कार्यों या ऑपरेटरों को अधिभार कर सकते हैं।
• अंकन। सी ++ में, यह नहीं है, लेकिन मठों के कार्यान्वयन के लिए इसकी आवश्यकता नहीं है, हालांकि यह उनके उपयोग को बहुत अधिक सुविधाजनक बनाता है। इसके एनालॉग को मानक में जोड़ने के लिए पहले से ही एक प्रस्ताव है, लेकिन नीचे उस पर और अधिक।

हास्केल के मोनाड को इस प्रकार परिभाषित किया गया है:

class Monad m where (>>= ) ::ma -> (a->mb)->mb (>> ) ::m a->m b->mb return ::a->ma fail::String->ma 

पहले, चलो कुछ सार संन्यासी लेते हैं, भले ही सी ++ में इसका प्रकार हो

 Monad. ,     . 
 template<typename A, typename B> Monad<B> operator>>=(Monad<A> ma, function<Monad<B> (A)> f) { ... //     }       ma,    f    f. 
 
 template<typename A, typename B> Monad<B> operator>>(Monad<A> ma, Monad<B> mb) { return Ma >>= [=](A){ return mb; }; }     >>= ,        .       ( m >> k = m >>= \_ -> k ),     Haskell  C++. 
 
 template<typename A> Monad <A> mreturn(A a) { ... //     }  return    C++,      mreturn.     ,     a       . 
  fail    ,        . 
 
 ,        C++,    -        .         - Maybe ,   .,     std::future .      C++11.   future       T ,     .   , ,   -   ,      ,   ,  ,      .    future      get . 
 template<class T> class future { public: ... T get(); //  get         ... }; 
   C++11    – std::async .      ,           std::future .       : future<int> result = async(f); //  -      f int a = result.get(); //    f    . 
        mreturn  >>=   std::future #include <future> using namespace std; template<typename A> future<A> mreturn(const A& a) { return async([=]{ return a; }); }  ,       future      ,   .     ,    . 
 
 template<typename A, typename B> future<B> operator>>=(future<A>& ma, const function<future<B> (A)>& f) { return async([&] () -> B { return f(ma.get()).get(); }); }   ,    ,         ma,       f,         f. 
 
  ,      .    3 ,     : Left identity : return a >>= f == fa Right identity: m >>= return == m Associativity: (m >>= f) >>= g == m >>= (\x -> fx >>= g) 
     C++, : 
 (mreturn(a) >>= f) == f(a)   , : 
 async([&] () -> B { return f(mreturn(a).get()).get(); }) == f(a) ,  mreturn(a).get()   ,   .     a  std::future ,     . , : 
 async([&] () -> B { return f(a).get(); }) == f(a)  ,  ,     f ,        .   ,   f  ,      (   ). 
 
  : m >>= mreturn == m   , : 
 async([&] () -> B { return mreturn(m.get()).get(); }) == m      mreturn(x).get() , : 
 async([&] () -> B { return m.get(); }) == m  ,     m.    ,        m. 
 
  : (m >>= f) >>= g == m >>= (\x -> fx >>= g)       ,   ,   .      m   f,   ,      m.       g,     f.     f  g             m. 
 
    .    -     : function<future<int> (int)> f = [](int a){ cout << a << '\n'; return mreturn(a + 6); }; int a = (mreturn(5) >>= f).get(); cout << a;   ,    5  11. 
 
  C++11      mreturn  >>=.      : n3721 
  mreturn  make_ready_future . 
  >>= ,    std::future   then .     ,       A ,   future.     ,        ,   future    ,   then ,   . 
     unwrap      future<future>  future.   join  Control.Monad  . 
 
  then     : future<int> f(shared_ptr<stream> str) { shared_ptr<vector<char>> buf = ...; return str->read(512, buf).then([](future<int> op) { return op.get() + 11; }); } future<void> g() { shared_ptr<stream> s = ...; return f(s).then([s](future<int> op) { s->close(); }); }     ,   ,          .       resumable : n3722 .        : future<int> f(stream str) resumable { shared_ptr<vector<char>> buf = ...; int count = await str.read(512, buf); return count + 11; } future<void> g() resumable { stream s = ...; int pls11 = await f(s); s.close(); }   resumable ,    ,    ,       .     await –     ( <- )  do   . ,   str.read  f    future,      await  int ,       . 
 
      ?  ,    ,      :           resumable ,  ,   Fibers  Windows  boost::coroutine .    ,     .     resumable   -     ,    await . ,   await    then       ,    await .    resumable     std::future ,          then  get .         C++,        ,    ,  ,   .            std::future . 
  ,    resumable       .        ,     resumable     . 

Monad. , .
template<typename A, typename B> Monad<B> operator>>=(Monad<A> ma, function<Monad<B> (A)> f) { ... // } ma, f f.

template<typename A, typename B> Monad<B> operator>>(Monad<A> ma, Monad<B> mb) { return Ma >>= [=](A){ return mb; }; } >>= , . ( m >> k = m >>= \_ -> k ), Haskell C++.

template<typename A> Monad <A> mreturn(A a) { ... // } return C++, mreturn. , a .
fail , .

, C++, - . - Maybe , ., std::future . C++11. future T , . , , - , , , , . future get .
template<class T> class future { public: ... T get(); // get ... };
C++11 – std::async . , std::future . : future<int> result = async(f); // - f int a = result.get(); // f .
mreturn >>= std::future #include <future> using namespace std; template<typename A> future<A> mreturn(const A& a) { return async([=]{ return a; }); } , future , . , .

template<typename A, typename B> future<B> operator>>=(future<A>& ma, const function<future<B> (A)>& f) { return async([&] () -> B { return f(ma.get()).get(); }); } , , ma, f, f.

, . 3 , : Left identity : return a >>= f == fa Right identity: m >>= return == m Associativity: (m >>= f) >>= g == m >>= (\x -> fx >>= g)
C++, :
(mreturn(a) >>= f) == f(a) , :
async([&] () -> B { return f(mreturn(a).get()).get(); }) == f(a) , mreturn(a).get() , . a std::future , . , :
async([&] () -> B { return f(a).get(); }) == f(a) , , f , . , f , ( ).

: m >>= mreturn == m , :
async([&] () -> B { return mreturn(m.get()).get(); }) == m mreturn(x).get() , :
async([&] () -> B { return m.get(); }) == m , m. , m.

: (m >>= f) >>= g == m >>= (\x -> fx >>= g) , , . m f, , m. g, f. f g m.

. - : function<future<int> (int)> f = [](int a){ cout << a << '\n'; return mreturn(a + 6); }; int a = (mreturn(5) >>= f).get(); cout << a; , 5 11.

C++11 mreturn >>=. : n3721
mreturn make_ready_future .
>>= , std::future then . , A , future. , , future , then , .
unwrap future<future> future. join Control.Monad .

then : future<int> f(shared_ptr<stream> str) { shared_ptr<vector<char>> buf = ...; return str->read(512, buf).then([](future<int> op) { return op.get() + 11; }); } future<void> g() { shared_ptr<stream> s = ...; return f(s).then([s](future<int> op) { s->close(); }); } , , . resumable : n3722 . : future<int> f(stream str) resumable { shared_ptr<vector<char>> buf = ...; int count = await str.read(512, buf); return count + 11; } future<void> g() resumable { stream s = ...; int pls11 = await f(s); s.close(); } resumable , , , . await – ( <- ) do . , str.read f future, await int , .

? , , : resumable , , Fibers Windows boost::coroutine . , . resumable - , await . , await then , await . resumable std::future , then get . C++, , , , . std::future .
, resumable . , resumable .

 Monad. ,     . 
 template<typename A, typename B> Monad<B> operator>>=(Monad<A> ma, function<Monad<B> (A)> f) { ... //     }       ma,    f    f. 
 
 template<typename A, typename B> Monad<B> operator>>(Monad<A> ma, Monad<B> mb) { return Ma >>= [=](A){ return mb; }; }     >>= ,        .       ( m >> k = m >>= \_ -> k ),     Haskell  C++. 
 
 template<typename A> Monad <A> mreturn(A a) { ... //     }  return    C++,      mreturn.     ,     a       . 
  fail    ,        . 
 
 ,        C++,    -        .         - Maybe ,   .,     std::future .      C++11.   future       T ,     .   , ,   -   ,      ,   ,  ,      .    future      get . 
 template<class T> class future { public: ... T get(); //  get         ... }; 
   C++11    – std::async .      ,           std::future .       : future<int> result = async(f); //  -      f int a = result.get(); //    f    . 
        mreturn  >>=   std::future #include <future> using namespace std; template<typename A> future<A> mreturn(const A& a) { return async([=]{ return a; }); }  ,       future      ,   .     ,    . 
 
 template<typename A, typename B> future<B> operator>>=(future<A>& ma, const function<future<B> (A)>& f) { return async([&] () -> B { return f(ma.get()).get(); }); }   ,    ,         ma,       f,         f. 
 
  ,      .    3 ,     : Left identity : return a >>= f == fa Right identity: m >>= return == m Associativity: (m >>= f) >>= g == m >>= (\x -> fx >>= g) 
     C++, : 
 (mreturn(a) >>= f) == f(a)   , : 
 async([&] () -> B { return f(mreturn(a).get()).get(); }) == f(a) ,  mreturn(a).get()   ,   .     a  std::future ,     . , : 
 async([&] () -> B { return f(a).get(); }) == f(a)  ,  ,     f ,        .   ,   f  ,      (   ). 
 
  : m >>= mreturn == m   , : 
 async([&] () -> B { return mreturn(m.get()).get(); }) == m      mreturn(x).get() , : 
 async([&] () -> B { return m.get(); }) == m  ,     m.    ,        m. 
 
  : (m >>= f) >>= g == m >>= (\x -> fx >>= g)       ,   ,   .      m   f,   ,      m.       g,     f.     f  g             m. 
 
    .    -     : function<future<int> (int)> f = [](int a){ cout << a << '\n'; return mreturn(a + 6); }; int a = (mreturn(5) >>= f).get(); cout << a;   ,    5  11. 
 
  C++11      mreturn  >>=.      : n3721 
  mreturn  make_ready_future . 
  >>= ,    std::future   then .     ,       A ,   future.     ,        ,   future    ,   then ,   . 
     unwrap      future<future>  future.   join  Control.Monad  . 
 
  then     : future<int> f(shared_ptr<stream> str) { shared_ptr<vector<char>> buf = ...; return str->read(512, buf).then([](future<int> op) { return op.get() + 11; }); } future<void> g() { shared_ptr<stream> s = ...; return f(s).then([s](future<int> op) { s->close(); }); }     ,   ,          .       resumable : n3722 .        : future<int> f(stream str) resumable { shared_ptr<vector<char>> buf = ...; int count = await str.read(512, buf); return count + 11; } future<void> g() resumable { stream s = ...; int pls11 = await f(s); s.close(); }   resumable ,    ,    ,       .     await –     ( <- )  do   . ,   str.read  f    future,      await  int ,       . 
 
      ?  ,    ,      :           resumable ,  ,   Fibers  Windows  boost::coroutine .    ,     .     resumable   -     ,    await . ,   await    then       ,    await .    resumable     std::future ,          then  get .         C++,        ,    ,  ,   .            std::future . 
  ,    resumable       .        ,     resumable     . 

Monad. , .
template<typename A, typename B> Monad<B> operator>>=(Monad<A> ma, function<Monad<B> (A)> f) { ... // } ma, f f.

template<typename A, typename B> Monad<B> operator>>(Monad<A> ma, Monad<B> mb) { return Ma >>= [=](A){ return mb; }; } >>= , . ( m >> k = m >>= \_ -> k ), Haskell C++.

template<typename A> Monad <A> mreturn(A a) { ... // } return C++, mreturn. , a .
fail , .

, C++, - . - Maybe , ., std::future . C++11. future T , . , , - , , , , . future get .
template<class T> class future { public: ... T get(); // get ... };
C++11 – std::async . , std::future . : future<int> result = async(f); // - f int a = result.get(); // f .
mreturn >>= std::future #include <future> using namespace std; template<typename A> future<A> mreturn(const A& a) { return async([=]{ return a; }); } , future , . , .

template<typename A, typename B> future<B> operator>>=(future<A>& ma, const function<future<B> (A)>& f) { return async([&] () -> B { return f(ma.get()).get(); }); } , , ma, f, f.

, . 3 , : Left identity : return a >>= f == fa Right identity: m >>= return == m Associativity: (m >>= f) >>= g == m >>= (\x -> fx >>= g)
C++, :
(mreturn(a) >>= f) == f(a) , :
async([&] () -> B { return f(mreturn(a).get()).get(); }) == f(a) , mreturn(a).get() , . a std::future , . , :
async([&] () -> B { return f(a).get(); }) == f(a) , , f , . , f , ( ).

: m >>= mreturn == m , :
async([&] () -> B { return mreturn(m.get()).get(); }) == m mreturn(x).get() , :
async([&] () -> B { return m.get(); }) == m , m. , m.

: (m >>= f) >>= g == m >>= (\x -> fx >>= g) , , . m f, , m. g, f. f g m.

. - : function<future<int> (int)> f = [](int a){ cout << a << '\n'; return mreturn(a + 6); }; int a = (mreturn(5) >>= f).get(); cout << a; , 5 11.

C++11 mreturn >>=. : n3721
mreturn make_ready_future .
>>= , std::future then . , A , future. , , future , then , .
unwrap future<future> future. join Control.Monad .

then : future<int> f(shared_ptr<stream> str) { shared_ptr<vector<char>> buf = ...; return str->read(512, buf).then([](future<int> op) { return op.get() + 11; }); } future<void> g() { shared_ptr<stream> s = ...; return f(s).then([s](future<int> op) { s->close(); }); } , , . resumable : n3722 . : future<int> f(stream str) resumable { shared_ptr<vector<char>> buf = ...; int count = await str.read(512, buf); return count + 11; } future<void> g() resumable { stream s = ...; int pls11 = await f(s); s.close(); } resumable , , , . await – ( <- ) do . , str.read f future, await int , .

? , , : resumable , , Fibers Windows boost::coroutine . , . resumable - , await . , await then , await . resumable std::future , then get . C++, , , , . std::future .
, resumable . , resumable .

 Monad. ,     . 
 template<typename A, typename B> Monad<B> operator>>=(Monad<A> ma, function<Monad<B> (A)> f) { ... //     }       ma,    f    f. 
 
 template<typename A, typename B> Monad<B> operator>>(Monad<A> ma, Monad<B> mb) { return Ma >>= [=](A){ return mb; }; }     >>= ,        .       ( m >> k = m >>= \_ -> k ),     Haskell  C++. 
 
 template<typename A> Monad <A> mreturn(A a) { ... //     }  return    C++,      mreturn.     ,     a       . 
  fail    ,        . 
 
 ,        C++,    -        .         - Maybe ,   .,     std::future .      C++11.   future       T ,     .   , ,   -   ,      ,   ,  ,      .    future      get . 
 template<class T> class future { public: ... T get(); //  get         ... }; 
   C++11    – std::async .      ,           std::future .       : future<int> result = async(f); //  -      f int a = result.get(); //    f    . 
        mreturn  >>=   std::future #include <future> using namespace std; template<typename A> future<A> mreturn(const A& a) { return async([=]{ return a; }); }  ,       future      ,   .     ,    . 
 
 template<typename A, typename B> future<B> operator>>=(future<A>& ma, const function<future<B> (A)>& f) { return async([&] () -> B { return f(ma.get()).get(); }); }   ,    ,         ma,       f,         f. 
 
  ,      .    3 ,     : Left identity : return a >>= f == fa Right identity: m >>= return == m Associativity: (m >>= f) >>= g == m >>= (\x -> fx >>= g) 
     C++, : 
 (mreturn(a) >>= f) == f(a)   , : 
 async([&] () -> B { return f(mreturn(a).get()).get(); }) == f(a) ,  mreturn(a).get()   ,   .     a  std::future ,     . , : 
 async([&] () -> B { return f(a).get(); }) == f(a)  ,  ,     f ,        .   ,   f  ,      (   ). 
 
  : m >>= mreturn == m   , : 
 async([&] () -> B { return mreturn(m.get()).get(); }) == m      mreturn(x).get() , : 
 async([&] () -> B { return m.get(); }) == m  ,     m.    ,        m. 
 
  : (m >>= f) >>= g == m >>= (\x -> fx >>= g)       ,   ,   .      m   f,   ,      m.       g,     f.     f  g             m. 
 
    .    -     : function<future<int> (int)> f = [](int a){ cout << a << '\n'; return mreturn(a + 6); }; int a = (mreturn(5) >>= f).get(); cout << a;   ,    5  11. 
 
  C++11      mreturn  >>=.      : n3721 
  mreturn  make_ready_future . 
  >>= ,    std::future   then .     ,       A ,   future.     ,        ,   future    ,   then ,   . 
     unwrap      future<future>  future.   join  Control.Monad  . 
 
  then     : future<int> f(shared_ptr<stream> str) { shared_ptr<vector<char>> buf = ...; return str->read(512, buf).then([](future<int> op) { return op.get() + 11; }); } future<void> g() { shared_ptr<stream> s = ...; return f(s).then([s](future<int> op) { s->close(); }); }     ,   ,          .       resumable : n3722 .        : future<int> f(stream str) resumable { shared_ptr<vector<char>> buf = ...; int count = await str.read(512, buf); return count + 11; } future<void> g() resumable { stream s = ...; int pls11 = await f(s); s.close(); }   resumable ,    ,    ,       .     await –     ( <- )  do   . ,   str.read  f    future,      await  int ,       . 
 
      ?  ,    ,      :           resumable ,  ,   Fibers  Windows  boost::coroutine .    ,     .     resumable   -     ,    await . ,   await    then       ,    await .    resumable     std::future ,          then  get .         C++,        ,    ,  ,   .            std::future . 
  ,    resumable       .        ,     resumable     . 

Monad. , .
template<typename A, typename B> Monad<B> operator>>=(Monad<A> ma, function<Monad<B> (A)> f) { ... // } ma, f f.

template<typename A, typename B> Monad<B> operator>>(Monad<A> ma, Monad<B> mb) { return Ma >>= [=](A){ return mb; }; } >>= , . ( m >> k = m >>= \_ -> k ), Haskell C++.

template<typename A> Monad <A> mreturn(A a) { ... // } return C++, mreturn. , a .
fail , .

, C++, - . - Maybe , ., std::future . C++11. future T , . , , - , , , , . future get .
template<class T> class future { public: ... T get(); // get ... };
C++11 – std::async . , std::future . : future<int> result = async(f); // - f int a = result.get(); // f .
mreturn >>= std::future #include <future> using namespace std; template<typename A> future<A> mreturn(const A& a) { return async([=]{ return a; }); } , future , . , .

template<typename A, typename B> future<B> operator>>=(future<A>& ma, const function<future<B> (A)>& f) { return async([&] () -> B { return f(ma.get()).get(); }); } , , ma, f, f.

, . 3 , : Left identity : return a >>= f == fa Right identity: m >>= return == m Associativity: (m >>= f) >>= g == m >>= (\x -> fx >>= g)
C++, :
(mreturn(a) >>= f) == f(a) , :
async([&] () -> B { return f(mreturn(a).get()).get(); }) == f(a) , mreturn(a).get() , . a std::future , . , :
async([&] () -> B { return f(a).get(); }) == f(a) , , f , . , f , ( ).

: m >>= mreturn == m , :
async([&] () -> B { return mreturn(m.get()).get(); }) == m mreturn(x).get() , :
async([&] () -> B { return m.get(); }) == m , m. , m.

: (m >>= f) >>= g == m >>= (\x -> fx >>= g) , , . m f, , m. g, f. f g m.

. - : function<future<int> (int)> f = [](int a){ cout << a << '\n'; return mreturn(a + 6); }; int a = (mreturn(5) >>= f).get(); cout << a; , 5 11.

C++11 mreturn >>=. : n3721
mreturn make_ready_future .
>>= , std::future then . , A , future. , , future , then , .
unwrap future<future> future. join Control.Monad .

then : future<int> f(shared_ptr<stream> str) { shared_ptr<vector<char>> buf = ...; return str->read(512, buf).then([](future<int> op) { return op.get() + 11; }); } future<void> g() { shared_ptr<stream> s = ...; return f(s).then([s](future<int> op) { s->close(); }); } , , . resumable : n3722 . : future<int> f(stream str) resumable { shared_ptr<vector<char>> buf = ...; int count = await str.read(512, buf); return count + 11; } future<void> g() resumable { stream s = ...; int pls11 = await f(s); s.close(); } resumable , , , . await – ( <- ) do . , str.read f future, await int , .

? , , : resumable , , Fibers Windows boost::coroutine . , . resumable - , await . , await then , await . resumable std::future , then get . C++, , , , . std::future .
, resumable . , resumable .

 Monad. ,     . 
 template<typename A, typename B> Monad<B> operator>>=(Monad<A> ma, function<Monad<B> (A)> f) { ... //     }       ma,    f    f. 
 
 template<typename A, typename B> Monad<B> operator>>(Monad<A> ma, Monad<B> mb) { return Ma >>= [=](A){ return mb; }; }     >>= ,        .       ( m >> k = m >>= \_ -> k ),     Haskell  C++. 
 
 template<typename A> Monad <A> mreturn(A a) { ... //     }  return    C++,      mreturn.     ,     a       . 
  fail    ,        . 
 
 ,        C++,    -        .         - Maybe ,   .,     std::future .      C++11.   future       T ,     .   , ,   -   ,      ,   ,  ,      .    future      get . 
 template<class T> class future { public: ... T get(); //  get         ... }; 
   C++11    – std::async .      ,           std::future .       : future<int> result = async(f); //  -      f int a = result.get(); //    f    . 
        mreturn  >>=   std::future #include <future> using namespace std; template<typename A> future<A> mreturn(const A& a) { return async([=]{ return a; }); }  ,       future      ,   .     ,    . 
 
 template<typename A, typename B> future<B> operator>>=(future<A>& ma, const function<future<B> (A)>& f) { return async([&] () -> B { return f(ma.get()).get(); }); }   ,    ,         ma,       f,         f. 
 
  ,      .    3 ,     : Left identity : return a >>= f == fa Right identity: m >>= return == m Associativity: (m >>= f) >>= g == m >>= (\x -> fx >>= g) 
     C++, : 
 (mreturn(a) >>= f) == f(a)   , : 
 async([&] () -> B { return f(mreturn(a).get()).get(); }) == f(a) ,  mreturn(a).get()   ,   .     a  std::future ,     . , : 
 async([&] () -> B { return f(a).get(); }) == f(a)  ,  ,     f ,        .   ,   f  ,      (   ). 
 
  : m >>= mreturn == m   , : 
 async([&] () -> B { return mreturn(m.get()).get(); }) == m      mreturn(x).get() , : 
 async([&] () -> B { return m.get(); }) == m  ,     m.    ,        m. 
 
  : (m >>= f) >>= g == m >>= (\x -> fx >>= g)       ,   ,   .      m   f,   ,      m.       g,     f.     f  g             m. 
 
    .    -     : function<future<int> (int)> f = [](int a){ cout << a << '\n'; return mreturn(a + 6); }; int a = (mreturn(5) >>= f).get(); cout << a;   ,    5  11. 
 
  C++11      mreturn  >>=.      : n3721 
  mreturn  make_ready_future . 
  >>= ,    std::future   then .     ,       A ,   future.     ,        ,   future    ,   then ,   . 
     unwrap      future<future>  future.   join  Control.Monad  . 
 
  then     : future<int> f(shared_ptr<stream> str) { shared_ptr<vector<char>> buf = ...; return str->read(512, buf).then([](future<int> op) { return op.get() + 11; }); } future<void> g() { shared_ptr<stream> s = ...; return f(s).then([s](future<int> op) { s->close(); }); }     ,   ,          .       resumable : n3722 .        : future<int> f(stream str) resumable { shared_ptr<vector<char>> buf = ...; int count = await str.read(512, buf); return count + 11; } future<void> g() resumable { stream s = ...; int pls11 = await f(s); s.close(); }   resumable ,    ,    ,       .     await –     ( <- )  do   . ,   str.read  f    future,      await  int ,       . 
 
      ?  ,    ,      :           resumable ,  ,   Fibers  Windows  boost::coroutine .    ,     .     resumable   -     ,    await . ,   await    then       ,    await .    resumable     std::future ,          then  get .         C++,        ,    ,  ,   .            std::future . 
  ,    resumable       .        ,     resumable     . 

Monad. , .
template<typename A, typename B> Monad<B> operator>>=(Monad<A> ma, function<Monad<B> (A)> f) { ... // } ma, f f.

template<typename A, typename B> Monad<B> operator>>(Monad<A> ma, Monad<B> mb) { return Ma >>= [=](A){ return mb; }; } >>= , . ( m >> k = m >>= \_ -> k ), Haskell C++.

template<typename A> Monad <A> mreturn(A a) { ... // } return C++, mreturn. , a .
fail , .

, C++, - . - Maybe , ., std::future . C++11. future T , . , , - , , , , . future get .
template<class T> class future { public: ... T get(); // get ... };
C++11 – std::async . , std::future . : future<int> result = async(f); // - f int a = result.get(); // f .
mreturn >>= std::future #include <future> using namespace std; template<typename A> future<A> mreturn(const A& a) { return async([=]{ return a; }); } , future , . , .

template<typename A, typename B> future<B> operator>>=(future<A>& ma, const function<future<B> (A)>& f) { return async([&] () -> B { return f(ma.get()).get(); }); } , , ma, f, f.

, . 3 , : Left identity : return a >>= f == fa Right identity: m >>= return == m Associativity: (m >>= f) >>= g == m >>= (\x -> fx >>= g)
C++, :
(mreturn(a) >>= f) == f(a) , :
async([&] () -> B { return f(mreturn(a).get()).get(); }) == f(a) , mreturn(a).get() , . a std::future , . , :
async([&] () -> B { return f(a).get(); }) == f(a) , , f , . , f , ( ).

: m >>= mreturn == m , :
async([&] () -> B { return mreturn(m.get()).get(); }) == m mreturn(x).get() , :
async([&] () -> B { return m.get(); }) == m , m. , m.

: (m >>= f) >>= g == m >>= (\x -> fx >>= g) , , . m f, , m. g, f. f g m.

. - : function<future<int> (int)> f = [](int a){ cout << a << '\n'; return mreturn(a + 6); }; int a = (mreturn(5) >>= f).get(); cout << a; , 5 11.

C++11 mreturn >>=. : n3721
mreturn make_ready_future .
>>= , std::future then . , A , future. , , future , then , .
unwrap future<future> future. join Control.Monad .

then : future<int> f(shared_ptr<stream> str) { shared_ptr<vector<char>> buf = ...; return str->read(512, buf).then([](future<int> op) { return op.get() + 11; }); } future<void> g() { shared_ptr<stream> s = ...; return f(s).then([s](future<int> op) { s->close(); }); } , , . resumable : n3722 . : future<int> f(stream str) resumable { shared_ptr<vector<char>> buf = ...; int count = await str.read(512, buf); return count + 11; } future<void> g() resumable { stream s = ...; int pls11 = await f(s); s.close(); } resumable , , , . await – ( <- ) do . , str.read f future, await int , .

? , , : resumable , , Fibers Windows boost::coroutine . , . resumable - , await . , await then , await . resumable std::future , then get . C++, , , , . std::future .
, resumable . , resumable .

 Monad. ,     . 
 template<typename A, typename B> Monad<B> operator>>=(Monad<A> ma, function<Monad<B> (A)> f) { ... //     }       ma,    f    f. 
 
 template<typename A, typename B> Monad<B> operator>>(Monad<A> ma, Monad<B> mb) { return Ma >>= [=](A){ return mb; }; }     >>= ,        .       ( m >> k = m >>= \_ -> k ),     Haskell  C++. 
 
 template<typename A> Monad <A> mreturn(A a) { ... //     }  return    C++,      mreturn.     ,     a       . 
  fail    ,        . 
 
 ,        C++,    -        .         - Maybe ,   .,     std::future .      C++11.   future       T ,     .   , ,   -   ,      ,   ,  ,      .    future      get . 
 template<class T> class future { public: ... T get(); //  get         ... }; 
   C++11    – std::async .      ,           std::future .       : future<int> result = async(f); //  -      f int a = result.get(); //    f    . 
        mreturn  >>=   std::future #include <future> using namespace std; template<typename A> future<A> mreturn(const A& a) { return async([=]{ return a; }); }  ,       future      ,   .     ,    . 
 
 template<typename A, typename B> future<B> operator>>=(future<A>& ma, const function<future<B> (A)>& f) { return async([&] () -> B { return f(ma.get()).get(); }); }   ,    ,         ma,       f,         f. 
 
  ,      .    3 ,     : Left identity : return a >>= f == fa Right identity: m >>= return == m Associativity: (m >>= f) >>= g == m >>= (\x -> fx >>= g) 
     C++, : 
 (mreturn(a) >>= f) == f(a)   , : 
 async([&] () -> B { return f(mreturn(a).get()).get(); }) == f(a) ,  mreturn(a).get()   ,   .     a  std::future ,     . , : 
 async([&] () -> B { return f(a).get(); }) == f(a)  ,  ,     f ,        .   ,   f  ,      (   ). 
 
  : m >>= mreturn == m   , : 
 async([&] () -> B { return mreturn(m.get()).get(); }) == m      mreturn(x).get() , : 
 async([&] () -> B { return m.get(); }) == m  ,     m.    ,        m. 
 
  : (m >>= f) >>= g == m >>= (\x -> fx >>= g)       ,   ,   .      m   f,   ,      m.       g,     f.     f  g             m. 
 
    .    -     : function<future<int> (int)> f = [](int a){ cout << a << '\n'; return mreturn(a + 6); }; int a = (mreturn(5) >>= f).get(); cout << a;   ,    5  11. 
 
  C++11      mreturn  >>=.      : n3721 
  mreturn  make_ready_future . 
  >>= ,    std::future   then .     ,       A ,   future.     ,        ,   future    ,   then ,   . 
     unwrap      future<future>  future.   join  Control.Monad  . 
 
  then     : future<int> f(shared_ptr<stream> str) { shared_ptr<vector<char>> buf = ...; return str->read(512, buf).then([](future<int> op) { return op.get() + 11; }); } future<void> g() { shared_ptr<stream> s = ...; return f(s).then([s](future<int> op) { s->close(); }); }     ,   ,          .       resumable : n3722 .        : future<int> f(stream str) resumable { shared_ptr<vector<char>> buf = ...; int count = await str.read(512, buf); return count + 11; } future<void> g() resumable { stream s = ...; int pls11 = await f(s); s.close(); }   resumable ,    ,    ,       .     await –     ( <- )  do   . ,   str.read  f    future,      await  int ,       . 
 
      ?  ,    ,      :           resumable ,  ,   Fibers  Windows  boost::coroutine .    ,     .     resumable   -     ,    await . ,   await    then       ,    await .    resumable     std::future ,          then  get .         C++,        ,    ,  ,   .            std::future . 
  ,    resumable       .        ,     resumable     . 

Monad. , .
template<typename A, typename B> Monad<B> operator>>=(Monad<A> ma, function<Monad<B> (A)> f) { ... // } ma, f f.

template<typename A, typename B> Monad<B> operator>>(Monad<A> ma, Monad<B> mb) { return Ma >>= [=](A){ return mb; }; } >>= , . ( m >> k = m >>= \_ -> k ), Haskell C++.

template<typename A> Monad <A> mreturn(A a) { ... // } return C++, mreturn. , a .
fail , .

, C++, - . - Maybe , ., std::future . C++11. future T , . , , - , , , , . future get .
template<class T> class future { public: ... T get(); // get ... };
C++11 – std::async . , std::future . : future<int> result = async(f); // - f int a = result.get(); // f .
mreturn >>= std::future #include <future> using namespace std; template<typename A> future<A> mreturn(const A& a) { return async([=]{ return a; }); } , future , . , .

template<typename A, typename B> future<B> operator>>=(future<A>& ma, const function<future<B> (A)>& f) { return async([&] () -> B { return f(ma.get()).get(); }); } , , ma, f, f.

, . 3 , : Left identity : return a >>= f == fa Right identity: m >>= return == m Associativity: (m >>= f) >>= g == m >>= (\x -> fx >>= g)
C++, :
(mreturn(a) >>= f) == f(a) , :
async([&] () -> B { return f(mreturn(a).get()).get(); }) == f(a) , mreturn(a).get() , . a std::future , . , :
async([&] () -> B { return f(a).get(); }) == f(a) , , f , . , f , ( ).

: m >>= mreturn == m , :
async([&] () -> B { return mreturn(m.get()).get(); }) == m mreturn(x).get() , :
async([&] () -> B { return m.get(); }) == m , m. , m.

: (m >>= f) >>= g == m >>= (\x -> fx >>= g) , , . m f, , m. g, f. f g m.

. - : function<future<int> (int)> f = [](int a){ cout << a << '\n'; return mreturn(a + 6); }; int a = (mreturn(5) >>= f).get(); cout << a; , 5 11.

C++11 mreturn >>=. : n3721
mreturn make_ready_future .
>>= , std::future then . , A , future. , , future , then , .
unwrap future<future> future. join Control.Monad .

then : future<int> f(shared_ptr<stream> str) { shared_ptr<vector<char>> buf = ...; return str->read(512, buf).then([](future<int> op) { return op.get() + 11; }); } future<void> g() { shared_ptr<stream> s = ...; return f(s).then([s](future<int> op) { s->close(); }); } , , . resumable : n3722 . : future<int> f(stream str) resumable { shared_ptr<vector<char>> buf = ...; int count = await str.read(512, buf); return count + 11; } future<void> g() resumable { stream s = ...; int pls11 = await f(s); s.close(); } resumable , , , . await – ( <- ) do . , str.read f future, await int , .

? , , : resumable , , Fibers Windows boost::coroutine . , . resumable - , await . , await then , await . resumable std::future , then get . C++, , , , . std::future .
, resumable . , resumable .

 Monad. ,     . 
 template<typename A, typename B> Monad<B> operator>>=(Monad<A> ma, function<Monad<B> (A)> f) { ... //     }       ma,    f    f. 
 
 template<typename A, typename B> Monad<B> operator>>(Monad<A> ma, Monad<B> mb) { return Ma >>= [=](A){ return mb; }; }     >>= ,        .       ( m >> k = m >>= \_ -> k ),     Haskell  C++. 
 
 template<typename A> Monad <A> mreturn(A a) { ... //     }  return    C++,      mreturn.     ,     a       . 
  fail    ,        . 
 
 ,        C++,    -        .         - Maybe ,   .,     std::future .      C++11.   future       T ,     .   , ,   -   ,      ,   ,  ,      .    future      get . 
 template<class T> class future { public: ... T get(); //  get         ... }; 
   C++11    – std::async .      ,           std::future .       : future<int> result = async(f); //  -      f int a = result.get(); //    f    . 
        mreturn  >>=   std::future #include <future> using namespace std; template<typename A> future<A> mreturn(const A& a) { return async([=]{ return a; }); }  ,       future      ,   .     ,    . 
 
 template<typename A, typename B> future<B> operator>>=(future<A>& ma, const function<future<B> (A)>& f) { return async([&] () -> B { return f(ma.get()).get(); }); }   ,    ,         ma,       f,         f. 
 
  ,      .    3 ,     : Left identity : return a >>= f == fa Right identity: m >>= return == m Associativity: (m >>= f) >>= g == m >>= (\x -> fx >>= g) 
     C++, : 
 (mreturn(a) >>= f) == f(a)   , : 
 async([&] () -> B { return f(mreturn(a).get()).get(); }) == f(a) ,  mreturn(a).get()   ,   .     a  std::future ,     . , : 
 async([&] () -> B { return f(a).get(); }) == f(a)  ,  ,     f ,        .   ,   f  ,      (   ). 
 
  : m >>= mreturn == m   , : 
 async([&] () -> B { return mreturn(m.get()).get(); }) == m      mreturn(x).get() , : 
 async([&] () -> B { return m.get(); }) == m  ,     m.    ,        m. 
 
  : (m >>= f) >>= g == m >>= (\x -> fx >>= g)       ,   ,   .      m   f,   ,      m.       g,     f.     f  g             m. 
 
    .    -     : function<future<int> (int)> f = [](int a){ cout << a << '\n'; return mreturn(a + 6); }; int a = (mreturn(5) >>= f).get(); cout << a;   ,    5  11. 
 
  C++11      mreturn  >>=.      : n3721 
  mreturn  make_ready_future . 
  >>= ,    std::future   then .     ,       A ,   future.     ,        ,   future    ,   then ,   . 
     unwrap      future<future>  future.   join  Control.Monad  . 
 
  then     : future<int> f(shared_ptr<stream> str) { shared_ptr<vector<char>> buf = ...; return str->read(512, buf).then([](future<int> op) { return op.get() + 11; }); } future<void> g() { shared_ptr<stream> s = ...; return f(s).then([s](future<int> op) { s->close(); }); }     ,   ,          .       resumable : n3722 .        : future<int> f(stream str) resumable { shared_ptr<vector<char>> buf = ...; int count = await str.read(512, buf); return count + 11; } future<void> g() resumable { stream s = ...; int pls11 = await f(s); s.close(); }   resumable ,    ,    ,       .     await –     ( <- )  do   . ,   str.read  f    future,      await  int ,       . 
 
      ?  ,    ,      :           resumable ,  ,   Fibers  Windows  boost::coroutine .    ,     .     resumable   -     ,    await . ,   await    then       ,    await .    resumable     std::future ,          then  get .         C++,        ,    ,  ,   .            std::future . 
  ,    resumable       .        ,     resumable     . 

Monad. , .
template<typename A, typename B> Monad<B> operator>>=(Monad<A> ma, function<Monad<B> (A)> f) { ... // } ma, f f.

template<typename A, typename B> Monad<B> operator>>(Monad<A> ma, Monad<B> mb) { return Ma >>= [=](A){ return mb; }; } >>= , . ( m >> k = m >>= \_ -> k ), Haskell C++.

template<typename A> Monad <A> mreturn(A a) { ... // } return C++, mreturn. , a .
fail , .

, C++, - . - Maybe , ., std::future . C++11. future T , . , , - , , , , . future get .
template<class T> class future { public: ... T get(); // get ... };
C++11 – std::async . , std::future . : future<int> result = async(f); // - f int a = result.get(); // f .
mreturn >>= std::future #include <future> using namespace std; template<typename A> future<A> mreturn(const A& a) { return async([=]{ return a; }); } , future , . , .

template<typename A, typename B> future<B> operator>>=(future<A>& ma, const function<future<B> (A)>& f) { return async([&] () -> B { return f(ma.get()).get(); }); } , , ma, f, f.

, . 3 , : Left identity : return a >>= f == fa Right identity: m >>= return == m Associativity: (m >>= f) >>= g == m >>= (\x -> fx >>= g)
C++, :
(mreturn(a) >>= f) == f(a) , :
async([&] () -> B { return f(mreturn(a).get()).get(); }) == f(a) , mreturn(a).get() , . a std::future , . , :
async([&] () -> B { return f(a).get(); }) == f(a) , , f , . , f , ( ).

: m >>= mreturn == m , :
async([&] () -> B { return mreturn(m.get()).get(); }) == m mreturn(x).get() , :
async([&] () -> B { return m.get(); }) == m , m. , m.

: (m >>= f) >>= g == m >>= (\x -> fx >>= g) , , . m f, , m. g, f. f g m.

. - : function<future<int> (int)> f = [](int a){ cout << a << '\n'; return mreturn(a + 6); }; int a = (mreturn(5) >>= f).get(); cout << a; , 5 11.

C++11 mreturn >>=. : n3721
mreturn make_ready_future .
>>= , std::future then . , A , future. , , future , then , .
unwrap future<future> future. join Control.Monad .

then : future<int> f(shared_ptr<stream> str) { shared_ptr<vector<char>> buf = ...; return str->read(512, buf).then([](future<int> op) { return op.get() + 11; }); } future<void> g() { shared_ptr<stream> s = ...; return f(s).then([s](future<int> op) { s->close(); }); } , , . resumable : n3722 . : future<int> f(stream str) resumable { shared_ptr<vector<char>> buf = ...; int count = await str.read(512, buf); return count + 11; } future<void> g() resumable { stream s = ...; int pls11 = await f(s); s.close(); } resumable , , , . await – ( <- ) do . , str.read f future, await int , .

? , , : resumable , , Fibers Windows boost::coroutine . , . resumable - , await . , await then , await . resumable std::future , then get . C++, , , , . std::future .
, resumable . , resumable .

 Monad. ,     . 
 template<typename A, typename B> Monad<B> operator>>=(Monad<A> ma, function<Monad<B> (A)> f) { ... //     }       ma,    f    f. 
 
 template<typename A, typename B> Monad<B> operator>>(Monad<A> ma, Monad<B> mb) { return Ma >>= [=](A){ return mb; }; }     >>= ,        .       ( m >> k = m >>= \_ -> k ),     Haskell  C++. 
 
 template<typename A> Monad <A> mreturn(A a) { ... //     }  return    C++,      mreturn.     ,     a       . 
  fail    ,        . 
 
 ,        C++,    -        .         - Maybe ,   .,     std::future .      C++11.   future       T ,     .   , ,   -   ,      ,   ,  ,      .    future      get . 
 template<class T> class future { public: ... T get(); //  get         ... }; 
   C++11    – std::async .      ,           std::future .       : future<int> result = async(f); //  -      f int a = result.get(); //    f    . 
        mreturn  >>=   std::future #include <future> using namespace std; template<typename A> future<A> mreturn(const A& a) { return async([=]{ return a; }); }  ,       future      ,   .     ,    . 
 
 template<typename A, typename B> future<B> operator>>=(future<A>& ma, const function<future<B> (A)>& f) { return async([&] () -> B { return f(ma.get()).get(); }); }   ,    ,         ma,       f,         f. 
 
  ,      .    3 ,     : Left identity : return a >>= f == fa Right identity: m >>= return == m Associativity: (m >>= f) >>= g == m >>= (\x -> fx >>= g) 
     C++, : 
 (mreturn(a) >>= f) == f(a)   , : 
 async([&] () -> B { return f(mreturn(a).get()).get(); }) == f(a) ,  mreturn(a).get()   ,   .     a  std::future ,     . , : 
 async([&] () -> B { return f(a).get(); }) == f(a)  ,  ,     f ,        .   ,   f  ,      (   ). 
 
  : m >>= mreturn == m   , : 
 async([&] () -> B { return mreturn(m.get()).get(); }) == m      mreturn(x).get() , : 
 async([&] () -> B { return m.get(); }) == m  ,     m.    ,        m. 
 
  : (m >>= f) >>= g == m >>= (\x -> fx >>= g)       ,   ,   .      m   f,   ,      m.       g,     f.     f  g             m. 
 
    .    -     : function<future<int> (int)> f = [](int a){ cout << a << '\n'; return mreturn(a + 6); }; int a = (mreturn(5) >>= f).get(); cout << a;   ,    5  11. 
 
  C++11      mreturn  >>=.      : n3721 
  mreturn  make_ready_future . 
  >>= ,    std::future   then .     ,       A ,   future.     ,        ,   future    ,   then ,   . 
     unwrap      future<future>  future.   join  Control.Monad  . 
 
  then     : future<int> f(shared_ptr<stream> str) { shared_ptr<vector<char>> buf = ...; return str->read(512, buf).then([](future<int> op) { return op.get() + 11; }); } future<void> g() { shared_ptr<stream> s = ...; return f(s).then([s](future<int> op) { s->close(); }); }     ,   ,          .       resumable : n3722 .        : future<int> f(stream str) resumable { shared_ptr<vector<char>> buf = ...; int count = await str.read(512, buf); return count + 11; } future<void> g() resumable { stream s = ...; int pls11 = await f(s); s.close(); }   resumable ,    ,    ,       .     await –     ( <- )  do   . ,   str.read  f    future,      await  int ,       . 
 
      ?  ,    ,      :           resumable ,  ,   Fibers  Windows  boost::coroutine .    ,     .     resumable   -     ,    await . ,   await    then       ,    await .    resumable     std::future ,          then  get .         C++,        ,    ,  ,   .            std::future . 
  ,    resumable       .        ,     resumable     . 

Monad. , .
template<typename A, typename B> Monad<B> operator>>=(Monad<A> ma, function<Monad<B> (A)> f) { ... // } ma, f f.

template<typename A, typename B> Monad<B> operator>>(Monad<A> ma, Monad<B> mb) { return Ma >>= [=](A){ return mb; }; } >>= , . ( m >> k = m >>= \_ -> k ), Haskell C++.

template<typename A> Monad <A> mreturn(A a) { ... // } return C++, mreturn. , a .
fail , .

, C++, - . - Maybe , ., std::future . C++11. future T , . , , - , , , , . future get .
template<class T> class future { public: ... T get(); // get ... };
C++11 – std::async . , std::future . : future<int> result = async(f); // - f int a = result.get(); // f .
mreturn >>= std::future #include <future> using namespace std; template<typename A> future<A> mreturn(const A& a) { return async([=]{ return a; }); } , future , . , .

template<typename A, typename B> future<B> operator>>=(future<A>& ma, const function<future<B> (A)>& f) { return async([&] () -> B { return f(ma.get()).get(); }); } , , ma, f, f.

, . 3 , : Left identity : return a >>= f == fa Right identity: m >>= return == m Associativity: (m >>= f) >>= g == m >>= (\x -> fx >>= g)
C++, :
(mreturn(a) >>= f) == f(a) , :
async([&] () -> B { return f(mreturn(a).get()).get(); }) == f(a) , mreturn(a).get() , . a std::future , . , :
async([&] () -> B { return f(a).get(); }) == f(a) , , f , . , f , ( ).

: m >>= mreturn == m , :
async([&] () -> B { return mreturn(m.get()).get(); }) == m mreturn(x).get() , :
async([&] () -> B { return m.get(); }) == m , m. , m.

: (m >>= f) >>= g == m >>= (\x -> fx >>= g) , , . m f, , m. g, f. f g m.

. - : function<future<int> (int)> f = [](int a){ cout << a << '\n'; return mreturn(a + 6); }; int a = (mreturn(5) >>= f).get(); cout << a; , 5 11.

C++11 mreturn >>=. : n3721
mreturn make_ready_future .
>>= , std::future then . , A , future. , , future , then , .
unwrap future<future> future. join Control.Monad .

then : future<int> f(shared_ptr<stream> str) { shared_ptr<vector<char>> buf = ...; return str->read(512, buf).then([](future<int> op) { return op.get() + 11; }); } future<void> g() { shared_ptr<stream> s = ...; return f(s).then([s](future<int> op) { s->close(); }); } , , . resumable : n3722 . : future<int> f(stream str) resumable { shared_ptr<vector<char>> buf = ...; int count = await str.read(512, buf); return count + 11; } future<void> g() resumable { stream s = ...; int pls11 = await f(s); s.close(); } resumable , , , . await – ( <- ) do . , str.read f future, await int , .

? , , : resumable , , Fibers Windows boost::coroutine . , . resumable - , await . , await then , await . resumable std::future , then get . C++, , , , . std::future .
, resumable . , resumable .

 Monad. ,     . 
 template<typename A, typename B> Monad<B> operator>>=(Monad<A> ma, function<Monad<B> (A)> f) { ... //     }       ma,    f    f. 
 
 template<typename A, typename B> Monad<B> operator>>(Monad<A> ma, Monad<B> mb) { return Ma >>= [=](A){ return mb; }; }     >>= ,        .       ( m >> k = m >>= \_ -> k ),     Haskell  C++. 
 
 template<typename A> Monad <A> mreturn(A a) { ... //     }  return    C++,      mreturn.     ,     a       . 
  fail    ,        . 
 
 ,        C++,    -        .         - Maybe ,   .,     std::future .      C++11.   future       T ,     .   , ,   -   ,      ,   ,  ,      .    future      get . 
 template<class T> class future { public: ... T get(); //  get         ... }; 
   C++11    – std::async .      ,           std::future .       : future<int> result = async(f); //  -      f int a = result.get(); //    f    . 
        mreturn  >>=   std::future #include <future> using namespace std; template<typename A> future<A> mreturn(const A& a) { return async([=]{ return a; }); }  ,       future      ,   .     ,    . 
 
 template<typename A, typename B> future<B> operator>>=(future<A>& ma, const function<future<B> (A)>& f) { return async([&] () -> B { return f(ma.get()).get(); }); }   ,    ,         ma,       f,         f. 
 
  ,      .    3 ,     : Left identity : return a >>= f == fa Right identity: m >>= return == m Associativity: (m >>= f) >>= g == m >>= (\x -> fx >>= g) 
     C++, : 
 (mreturn(a) >>= f) == f(a)   , : 
 async([&] () -> B { return f(mreturn(a).get()).get(); }) == f(a) ,  mreturn(a).get()   ,   .     a  std::future ,     . , : 
 async([&] () -> B { return f(a).get(); }) == f(a)  ,  ,     f ,        .   ,   f  ,      (   ). 
 
  : m >>= mreturn == m   , : 
 async([&] () -> B { return mreturn(m.get()).get(); }) == m      mreturn(x).get() , : 
 async([&] () -> B { return m.get(); }) == m  ,     m.    ,        m. 
 
  : (m >>= f) >>= g == m >>= (\x -> fx >>= g)       ,   ,   .      m   f,   ,      m.       g,     f.     f  g             m. 
 
    .    -     : function<future<int> (int)> f = [](int a){ cout << a << '\n'; return mreturn(a + 6); }; int a = (mreturn(5) >>= f).get(); cout << a;   ,    5  11. 
 
  C++11      mreturn  >>=.      : n3721 
  mreturn  make_ready_future . 
  >>= ,    std::future   then .     ,       A ,   future.     ,        ,   future    ,   then ,   . 
     unwrap      future<future>  future.   join  Control.Monad  . 
 
  then     : future<int> f(shared_ptr<stream> str) { shared_ptr<vector<char>> buf = ...; return str->read(512, buf).then([](future<int> op) { return op.get() + 11; }); } future<void> g() { shared_ptr<stream> s = ...; return f(s).then([s](future<int> op) { s->close(); }); }     ,   ,          .       resumable : n3722 .        : future<int> f(stream str) resumable { shared_ptr<vector<char>> buf = ...; int count = await str.read(512, buf); return count + 11; } future<void> g() resumable { stream s = ...; int pls11 = await f(s); s.close(); }   resumable ,    ,    ,       .     await –     ( <- )  do   . ,   str.read  f    future,      await  int ,       . 
 
      ?  ,    ,      :           resumable ,  ,   Fibers  Windows  boost::coroutine .    ,     .     resumable   -     ,    await . ,   await    then       ,    await .    resumable     std::future ,          then  get .         C++,        ,    ,  ,   .            std::future . 
  ,    resumable       .        ,     resumable     . 

Monad. , .
template<typename A, typename B> Monad<B> operator>>=(Monad<A> ma, function<Monad<B> (A)> f) { ... // } ma, f f.

template<typename A, typename B> Monad<B> operator>>(Monad<A> ma, Monad<B> mb) { return Ma >>= [=](A){ return mb; }; } >>= , . ( m >> k = m >>= \_ -> k ), Haskell C++.

template<typename A> Monad <A> mreturn(A a) { ... // } return C++, mreturn. , a .
fail , .

, C++, - . - Maybe , ., std::future . C++11. future T , . , , - , , , , . future get .
template<class T> class future { public: ... T get(); // get ... };
C++11 – std::async . , std::future . : future<int> result = async(f); // - f int a = result.get(); // f .
mreturn >>= std::future #include <future> using namespace std; template<typename A> future<A> mreturn(const A& a) { return async([=]{ return a; }); } , future , . , .

template<typename A, typename B> future<B> operator>>=(future<A>& ma, const function<future<B> (A)>& f) { return async([&] () -> B { return f(ma.get()).get(); }); } , , ma, f, f.

, . 3 , : Left identity : return a >>= f == fa Right identity: m >>= return == m Associativity: (m >>= f) >>= g == m >>= (\x -> fx >>= g)
C++, :
(mreturn(a) >>= f) == f(a) , :
async([&] () -> B { return f(mreturn(a).get()).get(); }) == f(a) , mreturn(a).get() , . a std::future , . , :
async([&] () -> B { return f(a).get(); }) == f(a) , , f , . , f , ( ).

: m >>= mreturn == m , :
async([&] () -> B { return mreturn(m.get()).get(); }) == m mreturn(x).get() , :
async([&] () -> B { return m.get(); }) == m , m. , m.

: (m >>= f) >>= g == m >>= (\x -> fx >>= g) , , . m f, , m. g, f. f g m.

. - : function<future<int> (int)> f = [](int a){ cout << a << '\n'; return mreturn(a + 6); }; int a = (mreturn(5) >>= f).get(); cout << a; , 5 11.

C++11 mreturn >>=. : n3721
mreturn make_ready_future .
>>= , std::future then . , A , future. , , future , then , .
unwrap future<future> future. join Control.Monad .

then : future<int> f(shared_ptr<stream> str) { shared_ptr<vector<char>> buf = ...; return str->read(512, buf).then([](future<int> op) { return op.get() + 11; }); } future<void> g() { shared_ptr<stream> s = ...; return f(s).then([s](future<int> op) { s->close(); }); } , , . resumable : n3722 . : future<int> f(stream str) resumable { shared_ptr<vector<char>> buf = ...; int count = await str.read(512, buf); return count + 11; } future<void> g() resumable { stream s = ...; int pls11 = await f(s); s.close(); } resumable , , , . await – ( <- ) do . , str.read f future, await int , .

? , , : resumable , , Fibers Windows boost::coroutine . , . resumable - , await . , await then , await . resumable std::future , then get . C++, , , , . std::future .
, resumable . , resumable .

 Monad. ,     . 
 template<typename A, typename B> Monad<B> operator>>=(Monad<A> ma, function<Monad<B> (A)> f) { ... //     }       ma,    f    f. 
 
 template<typename A, typename B> Monad<B> operator>>(Monad<A> ma, Monad<B> mb) { return Ma >>= [=](A){ return mb; }; }     >>= ,        .       ( m >> k = m >>= \_ -> k ),     Haskell  C++. 
 
 template<typename A> Monad <A> mreturn(A a) { ... //     }  return    C++,      mreturn.     ,     a       . 
  fail    ,        . 
 
 ,        C++,    -        .         - Maybe ,   .,     std::future .      C++11.   future       T ,     .   , ,   -   ,      ,   ,  ,      .    future      get . 
 template<class T> class future { public: ... T get(); //  get         ... }; 
   C++11    – std::async .      ,           std::future .       : future<int> result = async(f); //  -      f int a = result.get(); //    f    . 
        mreturn  >>=   std::future #include <future> using namespace std; template<typename A> future<A> mreturn(const A& a) { return async([=]{ return a; }); }  ,       future      ,   .     ,    . 
 
 template<typename A, typename B> future<B> operator>>=(future<A>& ma, const function<future<B> (A)>& f) { return async([&] () -> B { return f(ma.get()).get(); }); }   ,    ,         ma,       f,         f. 
 
  ,      .    3 ,     : Left identity : return a >>= f == fa Right identity: m >>= return == m Associativity: (m >>= f) >>= g == m >>= (\x -> fx >>= g) 
     C++, : 
 (mreturn(a) >>= f) == f(a)   , : 
 async([&] () -> B { return f(mreturn(a).get()).get(); }) == f(a) ,  mreturn(a).get()   ,   .     a  std::future ,     . , : 
 async([&] () -> B { return f(a).get(); }) == f(a)  ,  ,     f ,        .   ,   f  ,      (   ). 
 
  : m >>= mreturn == m   , : 
 async([&] () -> B { return mreturn(m.get()).get(); }) == m      mreturn(x).get() , : 
 async([&] () -> B { return m.get(); }) == m  ,     m.    ,        m. 
 
  : (m >>= f) >>= g == m >>= (\x -> fx >>= g)       ,   ,   .      m   f,   ,      m.       g,     f.     f  g             m. 
 
    .    -     : function<future<int> (int)> f = [](int a){ cout << a << '\n'; return mreturn(a + 6); }; int a = (mreturn(5) >>= f).get(); cout << a;   ,    5  11. 
 
  C++11      mreturn  >>=.      : n3721 
  mreturn  make_ready_future . 
  >>= ,    std::future   then .     ,       A ,   future.     ,        ,   future    ,   then ,   . 
     unwrap      future<future>  future.   join  Control.Monad  . 
 
  then     : future<int> f(shared_ptr<stream> str) { shared_ptr<vector<char>> buf = ...; return str->read(512, buf).then([](future<int> op) { return op.get() + 11; }); } future<void> g() { shared_ptr<stream> s = ...; return f(s).then([s](future<int> op) { s->close(); }); }     ,   ,          .       resumable : n3722 .        : future<int> f(stream str) resumable { shared_ptr<vector<char>> buf = ...; int count = await str.read(512, buf); return count + 11; } future<void> g() resumable { stream s = ...; int pls11 = await f(s); s.close(); }   resumable ,    ,    ,       .     await –     ( <- )  do   . ,   str.read  f    future,      await  int ,       . 
 
      ?  ,    ,      :           resumable ,  ,   Fibers  Windows  boost::coroutine .    ,     .     resumable   -     ,    await . ,   await    then       ,    await .    resumable     std::future ,          then  get .         C++,        ,    ,  ,   .            std::future . 
  ,    resumable       .        ,     resumable     . 

Monad. , .
template<typename A, typename B> Monad<B> operator>>=(Monad<A> ma, function<Monad<B> (A)> f) { ... // } ma, f f.

template<typename A, typename B> Monad<B> operator>>(Monad<A> ma, Monad<B> mb) { return Ma >>= [=](A){ return mb; }; } >>= , . ( m >> k = m >>= \_ -> k ), Haskell C++.

template<typename A> Monad <A> mreturn(A a) { ... // } return C++, mreturn. , a .
fail , .

, C++, - . - Maybe , ., std::future . C++11. future T , . , , - , , , , . future get .
template<class T> class future { public: ... T get(); // get ... };
C++11 – std::async . , std::future . : future<int> result = async(f); // - f int a = result.get(); // f .
mreturn >>= std::future #include <future> using namespace std; template<typename A> future<A> mreturn(const A& a) { return async([=]{ return a; }); } , future , . , .

template<typename A, typename B> future<B> operator>>=(future<A>& ma, const function<future<B> (A)>& f) { return async([&] () -> B { return f(ma.get()).get(); }); } , , ma, f, f.

, . 3 , : Left identity : return a >>= f == fa Right identity: m >>= return == m Associativity: (m >>= f) >>= g == m >>= (\x -> fx >>= g)
C++, :
(mreturn(a) >>= f) == f(a) , :
async([&] () -> B { return f(mreturn(a).get()).get(); }) == f(a) , mreturn(a).get() , . a std::future , . , :
async([&] () -> B { return f(a).get(); }) == f(a) , , f , . , f , ( ).

: m >>= mreturn == m , :
async([&] () -> B { return mreturn(m.get()).get(); }) == m mreturn(x).get() , :
async([&] () -> B { return m.get(); }) == m , m. , m.

: (m >>= f) >>= g == m >>= (\x -> fx >>= g) , , . m f, , m. g, f. f g m.

. - : function<future<int> (int)> f = [](int a){ cout << a << '\n'; return mreturn(a + 6); }; int a = (mreturn(5) >>= f).get(); cout << a; , 5 11.

C++11 mreturn >>=. : n3721
mreturn make_ready_future .
>>= , std::future then . , A , future. , , future , then , .
unwrap future<future> future. join Control.Monad .

then : future<int> f(shared_ptr<stream> str) { shared_ptr<vector<char>> buf = ...; return str->read(512, buf).then([](future<int> op) { return op.get() + 11; }); } future<void> g() { shared_ptr<stream> s = ...; return f(s).then([s](future<int> op) { s->close(); }); } , , . resumable : n3722 . : future<int> f(stream str) resumable { shared_ptr<vector<char>> buf = ...; int count = await str.read(512, buf); return count + 11; } future<void> g() resumable { stream s = ...; int pls11 = await f(s); s.close(); } resumable , , , . await – ( <- ) do . , str.read f future, await int , .

? , , : resumable , , Fibers Windows boost::coroutine . , . resumable - , await . , await then , await . resumable std::future , then get . C++, , , , . std::future .
, resumable . , resumable .

 Monad. ,     . 
 template<typename A, typename B> Monad<B> operator>>=(Monad<A> ma, function<Monad<B> (A)> f) { ... //     }       ma,    f    f. 
 
 template<typename A, typename B> Monad<B> operator>>(Monad<A> ma, Monad<B> mb) { return Ma >>= [=](A){ return mb; }; }     >>= ,        .       ( m >> k = m >>= \_ -> k ),     Haskell  C++. 
 
 template<typename A> Monad <A> mreturn(A a) { ... //     }  return    C++,      mreturn.     ,     a       . 
  fail    ,        . 
 
 ,        C++,    -        .         - Maybe ,   .,     std::future .      C++11.   future       T ,     .   , ,   -   ,      ,   ,  ,      .    future      get . 
 template<class T> class future { public: ... T get(); //  get         ... }; 
   C++11    – std::async .      ,           std::future .       : future<int> result = async(f); //  -      f int a = result.get(); //    f    . 
        mreturn  >>=   std::future #include <future> using namespace std; template<typename A> future<A> mreturn(const A& a) { return async([=]{ return a; }); }  ,       future      ,   .     ,    . 
 
 template<typename A, typename B> future<B> operator>>=(future<A>& ma, const function<future<B> (A)>& f) { return async([&] () -> B { return f(ma.get()).get(); }); }   ,    ,         ma,       f,         f. 
 
  ,      .    3 ,     : Left identity : return a >>= f == fa Right identity: m >>= return == m Associativity: (m >>= f) >>= g == m >>= (\x -> fx >>= g) 
     C++, : 
 (mreturn(a) >>= f) == f(a)   , : 
 async([&] () -> B { return f(mreturn(a).get()).get(); }) == f(a) ,  mreturn(a).get()   ,   .     a  std::future ,     . , : 
 async([&] () -> B { return f(a).get(); }) == f(a)  ,  ,     f ,        .   ,   f  ,      (   ). 
 
  : m >>= mreturn == m   , : 
 async([&] () -> B { return mreturn(m.get()).get(); }) == m      mreturn(x).get() , : 
 async([&] () -> B { return m.get(); }) == m  ,     m.    ,        m. 
 
  : (m >>= f) >>= g == m >>= (\x -> fx >>= g)       ,   ,   .      m   f,   ,      m.       g,     f.     f  g             m. 
 
    .    -     : function<future<int> (int)> f = [](int a){ cout << a << '\n'; return mreturn(a + 6); }; int a = (mreturn(5) >>= f).get(); cout << a;   ,    5  11. 
 
  C++11      mreturn  >>=.      : n3721 
  mreturn  make_ready_future . 
  >>= ,    std::future   then .     ,       A ,   future.     ,        ,   future    ,   then ,   . 
     unwrap      future<future>  future.   join  Control.Monad  . 
 
  then     : future<int> f(shared_ptr<stream> str) { shared_ptr<vector<char>> buf = ...; return str->read(512, buf).then([](future<int> op) { return op.get() + 11; }); } future<void> g() { shared_ptr<stream> s = ...; return f(s).then([s](future<int> op) { s->close(); }); }     ,   ,          .       resumable : n3722 .        : future<int> f(stream str) resumable { shared_ptr<vector<char>> buf = ...; int count = await str.read(512, buf); return count + 11; } future<void> g() resumable { stream s = ...; int pls11 = await f(s); s.close(); }   resumable ,    ,    ,       .     await –     ( <- )  do   . ,   str.read  f    future,      await  int ,       . 
 
      ?  ,    ,      :           resumable ,  ,   Fibers  Windows  boost::coroutine .    ,     .     resumable   -     ,    await . ,   await    then       ,    await .    resumable     std::future ,          then  get .         C++,        ,    ,  ,   .            std::future . 
  ,    resumable       .        ,     resumable     . 

Monad. , .
template<typename A, typename B> Monad<B> operator>>=(Monad<A> ma, function<Monad<B> (A)> f) { ... // } ma, f f.

template<typename A, typename B> Monad<B> operator>>(Monad<A> ma, Monad<B> mb) { return Ma >>= [=](A){ return mb; }; } >>= , . ( m >> k = m >>= \_ -> k ), Haskell C++.

template<typename A> Monad <A> mreturn(A a) { ... // } return C++, mreturn. , a .
fail , .

, C++, - . - Maybe , ., std::future . C++11. future T , . , , - , , , , . future get .
template<class T> class future { public: ... T get(); // get ... };
C++11 – std::async . , std::future . : future<int> result = async(f); // - f int a = result.get(); // f .
mreturn >>= std::future #include <future> using namespace std; template<typename A> future<A> mreturn(const A& a) { return async([=]{ return a; }); } , future , . , .

template<typename A, typename B> future<B> operator>>=(future<A>& ma, const function<future<B> (A)>& f) { return async([&] () -> B { return f(ma.get()).get(); }); } , , ma, f, f.

, . 3 , : Left identity : return a >>= f == fa Right identity: m >>= return == m Associativity: (m >>= f) >>= g == m >>= (\x -> fx >>= g)
C++, :
(mreturn(a) >>= f) == f(a) , :
async([&] () -> B { return f(mreturn(a).get()).get(); }) == f(a) , mreturn(a).get() , . a std::future , . , :
async([&] () -> B { return f(a).get(); }) == f(a) , , f , . , f , ( ).

: m >>= mreturn == m , :
async([&] () -> B { return mreturn(m.get()).get(); }) == m mreturn(x).get() , :
async([&] () -> B { return m.get(); }) == m , m. , m.

: (m >>= f) >>= g == m >>= (\x -> fx >>= g) , , . m f, , m. g, f. f g m.

. - : function<future<int> (int)> f = [](int a){ cout << a << '\n'; return mreturn(a + 6); }; int a = (mreturn(5) >>= f).get(); cout << a; , 5 11.

C++11 mreturn >>=. : n3721
mreturn make_ready_future .
>>= , std::future then . , A , future. , , future , then , .
unwrap future<future> future. join Control.Monad .

then : future<int> f(shared_ptr<stream> str) { shared_ptr<vector<char>> buf = ...; return str->read(512, buf).then([](future<int> op) { return op.get() + 11; }); } future<void> g() { shared_ptr<stream> s = ...; return f(s).then([s](future<int> op) { s->close(); }); } , , . resumable : n3722 . : future<int> f(stream str) resumable { shared_ptr<vector<char>> buf = ...; int count = await str.read(512, buf); return count + 11; } future<void> g() resumable { stream s = ...; int pls11 = await f(s); s.close(); } resumable , , , . await – ( <- ) do . , str.read f future, await int , .

? , , : resumable , , Fibers Windows boost::coroutine . , . resumable - , await . , await then , await . resumable std::future , then get . C++, , , , . std::future .
, resumable . , resumable .

 Monad. ,     . 
 template<typename A, typename B> Monad<B> operator>>=(Monad<A> ma, function<Monad<B> (A)> f) { ... //     }       ma,    f    f. 
 
 template<typename A, typename B> Monad<B> operator>>(Monad<A> ma, Monad<B> mb) { return Ma >>= [=](A){ return mb; }; }     >>= ,        .       ( m >> k = m >>= \_ -> k ),     Haskell  C++. 
 
 template<typename A> Monad <A> mreturn(A a) { ... //     }  return    C++,      mreturn.     ,     a       . 
  fail    ,        . 
 
 ,        C++,    -        .         - Maybe ,   .,     std::future .      C++11.   future       T ,     .   , ,   -   ,      ,   ,  ,      .    future      get . 
 template<class T> class future { public: ... T get(); //  get         ... }; 
   C++11    – std::async .      ,           std::future .       : future<int> result = async(f); //  -      f int a = result.get(); //    f    . 
        mreturn  >>=   std::future #include <future> using namespace std; template<typename A> future<A> mreturn(const A& a) { return async([=]{ return a; }); }  ,       future      ,   .     ,    . 
 
 template<typename A, typename B> future<B> operator>>=(future<A>& ma, const function<future<B> (A)>& f) { return async([&] () -> B { return f(ma.get()).get(); }); }   ,    ,         ma,       f,         f. 
 
  ,      .    3 ,     : Left identity : return a >>= f == fa Right identity: m >>= return == m Associativity: (m >>= f) >>= g == m >>= (\x -> fx >>= g) 
     C++, : 
 (mreturn(a) >>= f) == f(a)   , : 
 async([&] () -> B { return f(mreturn(a).get()).get(); }) == f(a) ,  mreturn(a).get()   ,   .     a  std::future ,     . , : 
 async([&] () -> B { return f(a).get(); }) == f(a)  ,  ,     f ,        .   ,   f  ,      (   ). 
 
  : m >>= mreturn == m   , : 
 async([&] () -> B { return mreturn(m.get()).get(); }) == m      mreturn(x).get() , : 
 async([&] () -> B { return m.get(); }) == m  ,     m.    ,        m. 
 
  : (m >>= f) >>= g == m >>= (\x -> fx >>= g)       ,   ,   .      m   f,   ,      m.       g,     f.     f  g             m. 
 
    .    -     : function<future<int> (int)> f = [](int a){ cout << a << '\n'; return mreturn(a + 6); }; int a = (mreturn(5) >>= f).get(); cout << a;   ,    5  11. 
 
  C++11      mreturn  >>=.      : n3721 
  mreturn  make_ready_future . 
  >>= ,    std::future   then .     ,       A ,   future.     ,        ,   future    ,   then ,   . 
     unwrap      future<future>  future.   join  Control.Monad  . 
 
  then     : future<int> f(shared_ptr<stream> str) { shared_ptr<vector<char>> buf = ...; return str->read(512, buf).then([](future<int> op) { return op.get() + 11; }); } future<void> g() { shared_ptr<stream> s = ...; return f(s).then([s](future<int> op) { s->close(); }); }     ,   ,          .       resumable : n3722 .        : future<int> f(stream str) resumable { shared_ptr<vector<char>> buf = ...; int count = await str.read(512, buf); return count + 11; } future<void> g() resumable { stream s = ...; int pls11 = await f(s); s.close(); }   resumable ,    ,    ,       .     await –     ( <- )  do   . ,   str.read  f    future,      await  int ,       . 
 
      ?  ,    ,      :           resumable ,  ,   Fibers  Windows  boost::coroutine .    ,     .     resumable   -     ,    await . ,   await    then       ,    await .    resumable     std::future ,          then  get .         C++,        ,    ,  ,   .            std::future . 
  ,    resumable       .        ,     resumable     . 

Monad. , .
template<typename A, typename B> Monad<B> operator>>=(Monad<A> ma, function<Monad<B> (A)> f) { ... // } ma, f f.

template<typename A, typename B> Monad<B> operator>>(Monad<A> ma, Monad<B> mb) { return Ma >>= [=](A){ return mb; }; } >>= , . ( m >> k = m >>= \_ -> k ), Haskell C++.

template<typename A> Monad <A> mreturn(A a) { ... // } return C++, mreturn. , a .
fail , .

, C++, - . - Maybe , ., std::future . C++11. future T , . , , - , , , , . future get .
template<class T> class future { public: ... T get(); // get ... };
C++11 – std::async . , std::future . : future<int> result = async(f); // - f int a = result.get(); // f .
mreturn >>= std::future #include <future> using namespace std; template<typename A> future<A> mreturn(const A& a) { return async([=]{ return a; }); } , future , . , .

template<typename A, typename B> future<B> operator>>=(future<A>& ma, const function<future<B> (A)>& f) { return async([&] () -> B { return f(ma.get()).get(); }); } , , ma, f, f.

, . 3 , : Left identity : return a >>= f == fa Right identity: m >>= return == m Associativity: (m >>= f) >>= g == m >>= (\x -> fx >>= g)
C++, :
(mreturn(a) >>= f) == f(a) , :
async([&] () -> B { return f(mreturn(a).get()).get(); }) == f(a) , mreturn(a).get() , . a std::future , . , :
async([&] () -> B { return f(a).get(); }) == f(a) , , f , . , f , ( ).

: m >>= mreturn == m , :
async([&] () -> B { return mreturn(m.get()).get(); }) == m mreturn(x).get() , :
async([&] () -> B { return m.get(); }) == m , m. , m.

: (m >>= f) >>= g == m >>= (\x -> fx >>= g) , , . m f, , m. g, f. f g m.

. - : function<future<int> (int)> f = [](int a){ cout << a << '\n'; return mreturn(a + 6); }; int a = (mreturn(5) >>= f).get(); cout << a; , 5 11.

C++11 mreturn >>=. : n3721
mreturn make_ready_future .
>>= , std::future then . , A , future. , , future , then , .
unwrap future<future> future. join Control.Monad .

then : future<int> f(shared_ptr<stream> str) { shared_ptr<vector<char>> buf = ...; return str->read(512, buf).then([](future<int> op) { return op.get() + 11; }); } future<void> g() { shared_ptr<stream> s = ...; return f(s).then([s](future<int> op) { s->close(); }); } , , . resumable : n3722 . : future<int> f(stream str) resumable { shared_ptr<vector<char>> buf = ...; int count = await str.read(512, buf); return count + 11; } future<void> g() resumable { stream s = ...; int pls11 = await f(s); s.close(); } resumable , , , . await – ( <- ) do . , str.read f future, await int , .

? , , : resumable , , Fibers Windows boost::coroutine . , . resumable - , await . , await then , await . resumable std::future , then get . C++, , , , . std::future .
, resumable . , resumable .

 Monad. ,     . 
 template<typename A, typename B> Monad<B> operator>>=(Monad<A> ma, function<Monad<B> (A)> f) { ... //     }       ma,    f    f. 
 
 template<typename A, typename B> Monad<B> operator>>(Monad<A> ma, Monad<B> mb) { return Ma >>= [=](A){ return mb; }; }     >>= ,        .       ( m >> k = m >>= \_ -> k ),     Haskell  C++. 
 
 template<typename A> Monad <A> mreturn(A a) { ... //     }  return    C++,      mreturn.     ,     a       . 
  fail    ,        . 
 
 ,        C++,    -        .         - Maybe ,   .,     std::future .      C++11.   future       T ,     .   , ,   -   ,      ,   ,  ,      .    future      get . 
 template<class T> class future { public: ... T get(); //  get         ... }; 
   C++11    – std::async .      ,           std::future .       : future<int> result = async(f); //  -      f int a = result.get(); //    f    . 
        mreturn  >>=   std::future #include <future> using namespace std; template<typename A> future<A> mreturn(const A& a) { return async([=]{ return a; }); }  ,       future      ,   .     ,    . 
 
 template<typename A, typename B> future<B> operator>>=(future<A>& ma, const function<future<B> (A)>& f) { return async([&] () -> B { return f(ma.get()).get(); }); }   ,    ,         ma,       f,         f. 
 
  ,      .    3 ,     : Left identity : return a >>= f == fa Right identity: m >>= return == m Associativity: (m >>= f) >>= g == m >>= (\x -> fx >>= g) 
     C++, : 
 (mreturn(a) >>= f) == f(a)   , : 
 async([&] () -> B { return f(mreturn(a).get()).get(); }) == f(a) ,  mreturn(a).get()   ,   .     a  std::future ,     . , : 
 async([&] () -> B { return f(a).get(); }) == f(a)  ,  ,     f ,        .   ,   f  ,      (   ). 
 
  : m >>= mreturn == m   , : 
 async([&] () -> B { return mreturn(m.get()).get(); }) == m      mreturn(x).get() , : 
 async([&] () -> B { return m.get(); }) == m  ,     m.    ,        m. 
 
  : (m >>= f) >>= g == m >>= (\x -> fx >>= g)       ,   ,   .      m   f,   ,      m.       g,     f.     f  g             m. 
 
    .    -     : function<future<int> (int)> f = [](int a){ cout << a << '\n'; return mreturn(a + 6); }; int a = (mreturn(5) >>= f).get(); cout << a;   ,    5  11. 
 
  C++11      mreturn  >>=.      : n3721 
  mreturn  make_ready_future . 
  >>= ,    std::future   then .     ,       A ,   future.     ,        ,   future    ,   then ,   . 
     unwrap      future<future>  future.   join  Control.Monad  . 
 
  then     : future<int> f(shared_ptr<stream> str) { shared_ptr<vector<char>> buf = ...; return str->read(512, buf).then([](future<int> op) { return op.get() + 11; }); } future<void> g() { shared_ptr<stream> s = ...; return f(s).then([s](future<int> op) { s->close(); }); }     ,   ,          .       resumable : n3722 .        : future<int> f(stream str) resumable { shared_ptr<vector<char>> buf = ...; int count = await str.read(512, buf); return count + 11; } future<void> g() resumable { stream s = ...; int pls11 = await f(s); s.close(); }   resumable ,    ,    ,       .     await –     ( <- )  do   . ,   str.read  f    future,      await  int ,       . 
 
      ?  ,    ,      :           resumable ,  ,   Fibers  Windows  boost::coroutine .    ,     .     resumable   -     ,    await . ,   await    then       ,    await .    resumable     std::future ,          then  get .         C++,        ,    ,  ,   .            std::future . 
  ,    resumable       .        ,     resumable     . 

Monad. , .
template<typename A, typename B> Monad<B> operator>>=(Monad<A> ma, function<Monad<B> (A)> f) { ... // } ma, f f.

template<typename A, typename B> Monad<B> operator>>(Monad<A> ma, Monad<B> mb) { return Ma >>= [=](A){ return mb; }; } >>= , . ( m >> k = m >>= \_ -> k ), Haskell C++.

template<typename A> Monad <A> mreturn(A a) { ... // } return C++, mreturn. , a .
fail , .

, C++, - . - Maybe , ., std::future . C++11. future T , . , , - , , , , . future get .
template<class T> class future { public: ... T get(); // get ... };
C++11 – std::async . , std::future . : future<int> result = async(f); // - f int a = result.get(); // f .
mreturn >>= std::future #include <future> using namespace std; template<typename A> future<A> mreturn(const A& a) { return async([=]{ return a; }); } , future , . , .

template<typename A, typename B> future<B> operator>>=(future<A>& ma, const function<future<B> (A)>& f) { return async([&] () -> B { return f(ma.get()).get(); }); } , , ma, f, f.

, . 3 , : Left identity : return a >>= f == fa Right identity: m >>= return == m Associativity: (m >>= f) >>= g == m >>= (\x -> fx >>= g)
C++, :
(mreturn(a) >>= f) == f(a) , :
async([&] () -> B { return f(mreturn(a).get()).get(); }) == f(a) , mreturn(a).get() , . a std::future , . , :
async([&] () -> B { return f(a).get(); }) == f(a) , , f , . , f , ( ).

: m >>= mreturn == m , :
async([&] () -> B { return mreturn(m.get()).get(); }) == m mreturn(x).get() , :
async([&] () -> B { return m.get(); }) == m , m. , m.

: (m >>= f) >>= g == m >>= (\x -> fx >>= g) , , . m f, , m. g, f. f g m.

. - : function<future<int> (int)> f = [](int a){ cout << a << '\n'; return mreturn(a + 6); }; int a = (mreturn(5) >>= f).get(); cout << a; , 5 11.

C++11 mreturn >>=. : n3721
mreturn make_ready_future .
>>= , std::future then . , A , future. , , future , then , .
unwrap future<future> future. join Control.Monad .

then : future<int> f(shared_ptr<stream> str) { shared_ptr<vector<char>> buf = ...; return str->read(512, buf).then([](future<int> op) { return op.get() + 11; }); } future<void> g() { shared_ptr<stream> s = ...; return f(s).then([s](future<int> op) { s->close(); }); } , , . resumable : n3722 . : future<int> f(stream str) resumable { shared_ptr<vector<char>> buf = ...; int count = await str.read(512, buf); return count + 11; } future<void> g() resumable { stream s = ...; int pls11 = await f(s); s.close(); } resumable , , , . await – ( <- ) do . , str.read f future, await int , .

? , , : resumable , , Fibers Windows boost::coroutine . , . resumable - , await . , await then , await . resumable std::future , then get . C++, , , , . std::future .
, resumable . , resumable .

 Monad. ,     . 
 template<typename A, typename B> Monad<B> operator>>=(Monad<A> ma, function<Monad<B> (A)> f) { ... //     }       ma,    f    f. 
 
 template<typename A, typename B> Monad<B> operator>>(Monad<A> ma, Monad<B> mb) { return Ma >>= [=](A){ return mb; }; }     >>= ,        .       ( m >> k = m >>= \_ -> k ),     Haskell  C++. 
 
 template<typename A> Monad <A> mreturn(A a) { ... //     }  return    C++,      mreturn.     ,     a       . 
  fail    ,        . 
 
 ,        C++,    -        .         - Maybe ,   .,     std::future .      C++11.   future       T ,     .   , ,   -   ,      ,   ,  ,      .    future      get . 
 template<class T> class future { public: ... T get(); //  get         ... }; 
   C++11    – std::async .      ,           std::future .       : future<int> result = async(f); //  -      f int a = result.get(); //    f    . 
        mreturn  >>=   std::future #include <future> using namespace std; template<typename A> future<A> mreturn(const A& a) { return async([=]{ return a; }); }  ,       future      ,   .     ,    . 
 
 template<typename A, typename B> future<B> operator>>=(future<A>& ma, const function<future<B> (A)>& f) { return async([&] () -> B { return f(ma.get()).get(); }); }   ,    ,         ma,       f,         f. 
 
  ,      .    3 ,     : Left identity : return a >>= f == fa Right identity: m >>= return == m Associativity: (m >>= f) >>= g == m >>= (\x -> fx >>= g) 
     C++, : 
 (mreturn(a) >>= f) == f(a)   , : 
 async([&] () -> B { return f(mreturn(a).get()).get(); }) == f(a) ,  mreturn(a).get()   ,   .     a  std::future ,     . , : 
 async([&] () -> B { return f(a).get(); }) == f(a)  ,  ,     f ,        .   ,   f  ,      (   ). 
 
  : m >>= mreturn == m   , : 
 async([&] () -> B { return mreturn(m.get()).get(); }) == m      mreturn(x).get() , : 
 async([&] () -> B { return m.get(); }) == m  ,     m.    ,        m. 
 
  : (m >>= f) >>= g == m >>= (\x -> fx >>= g)       ,   ,   .      m   f,   ,      m.       g,     f.     f  g             m. 
 
    .    -     : function<future<int> (int)> f = [](int a){ cout << a << '\n'; return mreturn(a + 6); }; int a = (mreturn(5) >>= f).get(); cout << a;   ,    5  11. 
 
  C++11      mreturn  >>=.      : n3721 
  mreturn  make_ready_future . 
  >>= ,    std::future   then .     ,       A ,   future.     ,        ,   future    ,   then ,   . 
     unwrap      future<future>  future.   join  Control.Monad  . 
 
  then     : future<int> f(shared_ptr<stream> str) { shared_ptr<vector<char>> buf = ...; return str->read(512, buf).then([](future<int> op) { return op.get() + 11; }); } future<void> g() { shared_ptr<stream> s = ...; return f(s).then([s](future<int> op) { s->close(); }); }     ,   ,          .       resumable : n3722 .        : future<int> f(stream str) resumable { shared_ptr<vector<char>> buf = ...; int count = await str.read(512, buf); return count + 11; } future<void> g() resumable { stream s = ...; int pls11 = await f(s); s.close(); }   resumable ,    ,    ,       .     await –     ( <- )  do   . ,   str.read  f    future,      await  int ,       . 
 
      ?  ,    ,      :           resumable ,  ,   Fibers  Windows  boost::coroutine .    ,     .     resumable   -     ,    await . ,   await    then       ,    await .    resumable     std::future ,          then  get .         C++,        ,    ,  ,   .            std::future . 
  ,    resumable       .        ,     resumable     . 

Monad. , .
template<typename A, typename B> Monad<B> operator>>=(Monad<A> ma, function<Monad<B> (A)> f) { ... // } ma, f f.

template<typename A, typename B> Monad<B> operator>>(Monad<A> ma, Monad<B> mb) { return Ma >>= [=](A){ return mb; }; } >>= , . ( m >> k = m >>= \_ -> k ), Haskell C++.

template<typename A> Monad <A> mreturn(A a) { ... // } return C++, mreturn. , a .
fail , .

, C++, - . - Maybe , ., std::future . C++11. future T , . , , - , , , , . future get .
template<class T> class future { public: ... T get(); // get ... };
C++11 – std::async . , std::future . : future<int> result = async(f); // - f int a = result.get(); // f .
mreturn >>= std::future #include <future> using namespace std; template<typename A> future<A> mreturn(const A& a) { return async([=]{ return a; }); } , future , . , .

template<typename A, typename B> future<B> operator>>=(future<A>& ma, const function<future<B> (A)>& f) { return async([&] () -> B { return f(ma.get()).get(); }); } , , ma, f, f.

, . 3 , : Left identity : return a >>= f == fa Right identity: m >>= return == m Associativity: (m >>= f) >>= g == m >>= (\x -> fx >>= g)
C++, :
(mreturn(a) >>= f) == f(a) , :
async([&] () -> B { return f(mreturn(a).get()).get(); }) == f(a) , mreturn(a).get() , . a std::future , . , :
async([&] () -> B { return f(a).get(); }) == f(a) , , f , . , f , ( ).

: m >>= mreturn == m , :
async([&] () -> B { return mreturn(m.get()).get(); }) == m mreturn(x).get() , :
async([&] () -> B { return m.get(); }) == m , m. , m.

: (m >>= f) >>= g == m >>= (\x -> fx >>= g) , , . m f, , m. g, f. f g m.

. - : function<future<int> (int)> f = [](int a){ cout << a << '\n'; return mreturn(a + 6); }; int a = (mreturn(5) >>= f).get(); cout << a; , 5 11.

C++11 mreturn >>=. : n3721
mreturn make_ready_future .
>>= , std::future then . , A , future. , , future , then , .
unwrap future<future> future. join Control.Monad .

then : future<int> f(shared_ptr<stream> str) { shared_ptr<vector<char>> buf = ...; return str->read(512, buf).then([](future<int> op) { return op.get() + 11; }); } future<void> g() { shared_ptr<stream> s = ...; return f(s).then([s](future<int> op) { s->close(); }); } , , . resumable : n3722 . : future<int> f(stream str) resumable { shared_ptr<vector<char>> buf = ...; int count = await str.read(512, buf); return count + 11; } future<void> g() resumable { stream s = ...; int pls11 = await f(s); s.close(); } resumable , , , . await – ( <- ) do . , str.read f future, await int , .

? , , : resumable , , Fibers Windows boost::coroutine . , . resumable - , await . , await then , await . resumable std::future , then get . C++, , , , . std::future .
, resumable . , resumable .

 Monad. ,     . 
 template<typename A, typename B> Monad<B> operator>>=(Monad<A> ma, function<Monad<B> (A)> f) { ... //     }       ma,    f    f. 
 
 template<typename A, typename B> Monad<B> operator>>(Monad<A> ma, Monad<B> mb) { return Ma >>= [=](A){ return mb; }; }     >>= ,        .       ( m >> k = m >>= \_ -> k ),     Haskell  C++. 
 
 template<typename A> Monad <A> mreturn(A a) { ... //     }  return    C++,      mreturn.     ,     a       . 
  fail    ,        . 
 
 ,        C++,    -        .         - Maybe ,   .,     std::future .      C++11.   future       T ,     .   , ,   -   ,      ,   ,  ,      .    future      get . 
 template<class T> class future { public: ... T get(); //  get         ... }; 
   C++11    – std::async .      ,           std::future .       : future<int> result = async(f); //  -      f int a = result.get(); //    f    . 
        mreturn  >>=   std::future #include <future> using namespace std; template<typename A> future<A> mreturn(const A& a) { return async([=]{ return a; }); }  ,       future      ,   .     ,    . 
 
 template<typename A, typename B> future<B> operator>>=(future<A>& ma, const function<future<B> (A)>& f) { return async([&] () -> B { return f(ma.get()).get(); }); }   ,    ,         ma,       f,         f. 
 
  ,      .    3 ,     : Left identity : return a >>= f == fa Right identity: m >>= return == m Associativity: (m >>= f) >>= g == m >>= (\x -> fx >>= g) 
     C++, : 
 (mreturn(a) >>= f) == f(a)   , : 
 async([&] () -> B { return f(mreturn(a).get()).get(); }) == f(a) ,  mreturn(a).get()   ,   .     a  std::future ,     . , : 
 async([&] () -> B { return f(a).get(); }) == f(a)  ,  ,     f ,        .   ,   f  ,      (   ). 
 
  : m >>= mreturn == m   , : 
 async([&] () -> B { return mreturn(m.get()).get(); }) == m      mreturn(x).get() , : 
 async([&] () -> B { return m.get(); }) == m  ,     m.    ,        m. 
 
  : (m >>= f) >>= g == m >>= (\x -> fx >>= g)       ,   ,   .      m   f,   ,      m.       g,     f.     f  g             m. 
 
    .    -     : function<future<int> (int)> f = [](int a){ cout << a << '\n'; return mreturn(a + 6); }; int a = (mreturn(5) >>= f).get(); cout << a;   ,    5  11. 
 
  C++11      mreturn  >>=.      : n3721 
  mreturn  make_ready_future . 
  >>= ,    std::future   then .     ,       A ,   future.     ,        ,   future    ,   then ,   . 
     unwrap      future<future>  future.   join  Control.Monad  . 
 
  then     : future<int> f(shared_ptr<stream> str) { shared_ptr<vector<char>> buf = ...; return str->read(512, buf).then([](future<int> op) { return op.get() + 11; }); } future<void> g() { shared_ptr<stream> s = ...; return f(s).then([s](future<int> op) { s->close(); }); }     ,   ,          .       resumable : n3722 .        : future<int> f(stream str) resumable { shared_ptr<vector<char>> buf = ...; int count = await str.read(512, buf); return count + 11; } future<void> g() resumable { stream s = ...; int pls11 = await f(s); s.close(); }   resumable ,    ,    ,       .     await –     ( <- )  do   . ,   str.read  f    future,      await  int ,       . 
 
      ?  ,    ,      :           resumable ,  ,   Fibers  Windows  boost::coroutine .    ,     .     resumable   -     ,    await . ,   await    then       ,    await .    resumable     std::future ,          then  get .         C++,        ,    ,  ,   .            std::future . 
  ,    resumable       .        ,     resumable     . 

Monad. , .
template<typename A, typename B> Monad<B> operator>>=(Monad<A> ma, function<Monad<B> (A)> f) { ... // } ma, f f.

template<typename A, typename B> Monad<B> operator>>(Monad<A> ma, Monad<B> mb) { return Ma >>= [=](A){ return mb; }; } >>= , . ( m >> k = m >>= \_ -> k ), Haskell C++.

template<typename A> Monad <A> mreturn(A a) { ... // } return C++, mreturn. , a .
fail , .

, C++, - . - Maybe , ., std::future . C++11. future T , . , , - , , , , . future get .
template<class T> class future { public: ... T get(); // get ... };
C++11 – std::async . , std::future . : future<int> result = async(f); // - f int a = result.get(); // f .
mreturn >>= std::future #include <future> using namespace std; template<typename A> future<A> mreturn(const A& a) { return async([=]{ return a; }); } , future , . , .

template<typename A, typename B> future<B> operator>>=(future<A>& ma, const function<future<B> (A)>& f) { return async([&] () -> B { return f(ma.get()).get(); }); } , , ma, f, f.

, . 3 , : Left identity : return a >>= f == fa Right identity: m >>= return == m Associativity: (m >>= f) >>= g == m >>= (\x -> fx >>= g)
C++, :
(mreturn(a) >>= f) == f(a) , :
async([&] () -> B { return f(mreturn(a).get()).get(); }) == f(a) , mreturn(a).get() , . a std::future , . , :
async([&] () -> B { return f(a).get(); }) == f(a) , , f , . , f , ( ).

: m >>= mreturn == m , :
async([&] () -> B { return mreturn(m.get()).get(); }) == m mreturn(x).get() , :
async([&] () -> B { return m.get(); }) == m , m. , m.

: (m >>= f) >>= g == m >>= (\x -> fx >>= g) , , . m f, , m. g, f. f g m.

. - : function<future<int> (int)> f = [](int a){ cout << a << '\n'; return mreturn(a + 6); }; int a = (mreturn(5) >>= f).get(); cout << a; , 5 11.

C++11 mreturn >>=. : n3721
mreturn make_ready_future .
>>= , std::future then . , A , future. , , future , then , .
unwrap future<future> future. join Control.Monad .

then : future<int> f(shared_ptr<stream> str) { shared_ptr<vector<char>> buf = ...; return str->read(512, buf).then([](future<int> op) { return op.get() + 11; }); } future<void> g() { shared_ptr<stream> s = ...; return f(s).then([s](future<int> op) { s->close(); }); } , , . resumable : n3722 . : future<int> f(stream str) resumable { shared_ptr<vector<char>> buf = ...; int count = await str.read(512, buf); return count + 11; } future<void> g() resumable { stream s = ...; int pls11 = await f(s); s.close(); } resumable , , , . await – ( <- ) do . , str.read f future, await int , .

? , , : resumable , , Fibers Windows boost::coroutine . , . resumable - , await . , await then , await . resumable std::future , then get . C++, , , , . std::future .
, resumable . , resumable .

 Monad. ,     . 
 template<typename A, typename B> Monad<B> operator>>=(Monad<A> ma, function<Monad<B> (A)> f) { ... //     }       ma,    f    f. 
 
 template<typename A, typename B> Monad<B> operator>>(Monad<A> ma, Monad<B> mb) { return Ma >>= [=](A){ return mb; }; }     >>= ,        .       ( m >> k = m >>= \_ -> k ),     Haskell  C++. 
 
 template<typename A> Monad <A> mreturn(A a) { ... //     }  return    C++,      mreturn.     ,     a       . 
  fail    ,        . 
 
 ,        C++,    -        .         - Maybe ,   .,     std::future .      C++11.   future       T ,     .   , ,   -   ,      ,   ,  ,      .    future      get . 
 template<class T> class future { public: ... T get(); //  get         ... }; 
   C++11    – std::async .      ,           std::future .       : future<int> result = async(f); //  -      f int a = result.get(); //    f    . 
        mreturn  >>=   std::future #include <future> using namespace std; template<typename A> future<A> mreturn(const A& a) { return async([=]{ return a; }); }  ,       future      ,   .     ,    . 
 
 template<typename A, typename B> future<B> operator>>=(future<A>& ma, const function<future<B> (A)>& f) { return async([&] () -> B { return f(ma.get()).get(); }); }   ,    ,         ma,       f,         f. 
 
  ,      .    3 ,     : Left identity : return a >>= f == fa Right identity: m >>= return == m Associativity: (m >>= f) >>= g == m >>= (\x -> fx >>= g) 
     C++, : 
 (mreturn(a) >>= f) == f(a)   , : 
 async([&] () -> B { return f(mreturn(a).get()).get(); }) == f(a) ,  mreturn(a).get()   ,   .     a  std::future ,     . , : 
 async([&] () -> B { return f(a).get(); }) == f(a)  ,  ,     f ,        .   ,   f  ,      (   ). 
 
  : m >>= mreturn == m   , : 
 async([&] () -> B { return mreturn(m.get()).get(); }) == m      mreturn(x).get() , : 
 async([&] () -> B { return m.get(); }) == m  ,     m.    ,        m. 
 
  : (m >>= f) >>= g == m >>= (\x -> fx >>= g)       ,   ,   .      m   f,   ,      m.       g,     f.     f  g             m. 
 
    .    -     : function<future<int> (int)> f = [](int a){ cout << a << '\n'; return mreturn(a + 6); }; int a = (mreturn(5) >>= f).get(); cout << a;   ,    5  11. 
 
  C++11      mreturn  >>=.      : n3721 
  mreturn  make_ready_future . 
  >>= ,    std::future   then .     ,       A ,   future.     ,        ,   future    ,   then ,   . 
     unwrap      future<future>  future.   join  Control.Monad  . 
 
  then     : future<int> f(shared_ptr<stream> str) { shared_ptr<vector<char>> buf = ...; return str->read(512, buf).then([](future<int> op) { return op.get() + 11; }); } future<void> g() { shared_ptr<stream> s = ...; return f(s).then([s](future<int> op) { s->close(); }); }     ,   ,          .       resumable : n3722 .        : future<int> f(stream str) resumable { shared_ptr<vector<char>> buf = ...; int count = await str.read(512, buf); return count + 11; } future<void> g() resumable { stream s = ...; int pls11 = await f(s); s.close(); }   resumable ,    ,    ,       .     await –     ( <- )  do   . ,   str.read  f    future,      await  int ,       . 
 
      ?  ,    ,      :           resumable ,  ,   Fibers  Windows  boost::coroutine .    ,     .     resumable   -     ,    await . ,   await    then       ,    await .    resumable     std::future ,          then  get .         C++,        ,    ,  ,   .            std::future . 
  ,    resumable       .        ,     resumable     . 

Monad. , .
template<typename A, typename B> Monad<B> operator>>=(Monad<A> ma, function<Monad<B> (A)> f) { ... // } ma, f f.

template<typename A, typename B> Monad<B> operator>>(Monad<A> ma, Monad<B> mb) { return Ma >>= [=](A){ return mb; }; } >>= , . ( m >> k = m >>= \_ -> k ), Haskell C++.

template<typename A> Monad <A> mreturn(A a) { ... // } return C++, mreturn. , a .
fail , .

, C++, - . - Maybe , ., std::future . C++11. future T , . , , - , , , , . future get .
template<class T> class future { public: ... T get(); // get ... };
C++11 – std::async . , std::future . : future<int> result = async(f); // - f int a = result.get(); // f .
mreturn >>= std::future #include <future> using namespace std; template<typename A> future<A> mreturn(const A& a) { return async([=]{ return a; }); } , future , . , .

template<typename A, typename B> future<B> operator>>=(future<A>& ma, const function<future<B> (A)>& f) { return async([&] () -> B { return f(ma.get()).get(); }); } , , ma, f, f.

, . 3 , : Left identity : return a >>= f == fa Right identity: m >>= return == m Associativity: (m >>= f) >>= g == m >>= (\x -> fx >>= g)
C++, :
(mreturn(a) >>= f) == f(a) , :
async([&] () -> B { return f(mreturn(a).get()).get(); }) == f(a) , mreturn(a).get() , . a std::future , . , :
async([&] () -> B { return f(a).get(); }) == f(a) , , f , . , f , ( ).

: m >>= mreturn == m , :
async([&] () -> B { return mreturn(m.get()).get(); }) == m mreturn(x).get() , :
async([&] () -> B { return m.get(); }) == m , m. , m.

: (m >>= f) >>= g == m >>= (\x -> fx >>= g) , , . m f, , m. g, f. f g m.

. - : function<future<int> (int)> f = [](int a){ cout << a << '\n'; return mreturn(a + 6); }; int a = (mreturn(5) >>= f).get(); cout << a; , 5 11.

C++11 mreturn >>=. : n3721
mreturn make_ready_future .
>>= , std::future then . , A , future. , , future , then , .
unwrap future<future> future. join Control.Monad .

then : future<int> f(shared_ptr<stream> str) { shared_ptr<vector<char>> buf = ...; return str->read(512, buf).then([](future<int> op) { return op.get() + 11; }); } future<void> g() { shared_ptr<stream> s = ...; return f(s).then([s](future<int> op) { s->close(); }); } , , . resumable : n3722 . : future<int> f(stream str) resumable { shared_ptr<vector<char>> buf = ...; int count = await str.read(512, buf); return count + 11; } future<void> g() resumable { stream s = ...; int pls11 = await f(s); s.close(); } resumable , , , . await – ( <- ) do . , str.read f future, await int , .

? , , : resumable , , Fibers Windows boost::coroutine . , . resumable - , await . , await then , await . resumable std::future , then get . C++, , , , . std::future .
, resumable . , resumable .

 Monad. ,     . 
 template<typename A, typename B> Monad<B> operator>>=(Monad<A> ma, function<Monad<B> (A)> f) { ... //     }       ma,    f    f. 
 
 template<typename A, typename B> Monad<B> operator>>(Monad<A> ma, Monad<B> mb) { return Ma >>= [=](A){ return mb; }; }     >>= ,        .       ( m >> k = m >>= \_ -> k ),     Haskell  C++. 
 
 template<typename A> Monad <A> mreturn(A a) { ... //     }  return    C++,      mreturn.     ,     a       . 
  fail    ,        . 
 
 ,        C++,    -        .         - Maybe ,   .,     std::future .      C++11.   future       T ,     .   , ,   -   ,      ,   ,  ,      .    future      get . 
 template<class T> class future { public: ... T get(); //  get         ... }; 
   C++11    – std::async .      ,           std::future .       : future<int> result = async(f); //  -      f int a = result.get(); //    f    . 
        mreturn  >>=   std::future #include <future> using namespace std; template<typename A> future<A> mreturn(const A& a) { return async([=]{ return a; }); }  ,       future      ,   .     ,    . 
 
 template<typename A, typename B> future<B> operator>>=(future<A>& ma, const function<future<B> (A)>& f) { return async([&] () -> B { return f(ma.get()).get(); }); }   ,    ,         ma,       f,         f. 
 
  ,      .    3 ,     : Left identity : return a >>= f == fa Right identity: m >>= return == m Associativity: (m >>= f) >>= g == m >>= (\x -> fx >>= g) 
     C++, : 
 (mreturn(a) >>= f) == f(a)   , : 
 async([&] () -> B { return f(mreturn(a).get()).get(); }) == f(a) ,  mreturn(a).get()   ,   .     a  std::future ,     . , : 
 async([&] () -> B { return f(a).get(); }) == f(a)  ,  ,     f ,        .   ,   f  ,      (   ). 
 
  : m >>= mreturn == m   , : 
 async([&] () -> B { return mreturn(m.get()).get(); }) == m      mreturn(x).get() , : 
 async([&] () -> B { return m.get(); }) == m  ,     m.    ,        m. 
 
  : (m >>= f) >>= g == m >>= (\x -> fx >>= g)       ,   ,   .      m   f,   ,      m.       g,     f.     f  g             m. 
 
    .    -     : function<future<int> (int)> f = [](int a){ cout << a << '\n'; return mreturn(a + 6); }; int a = (mreturn(5) >>= f).get(); cout << a;   ,    5  11. 
 
  C++11      mreturn  >>=.      : n3721 
  mreturn  make_ready_future . 
  >>= ,    std::future   then .     ,       A ,   future.     ,        ,   future    ,   then ,   . 
     unwrap      future<future>  future.   join  Control.Monad  . 
 
  then     : future<int> f(shared_ptr<stream> str) { shared_ptr<vector<char>> buf = ...; return str->read(512, buf).then([](future<int> op) { return op.get() + 11; }); } future<void> g() { shared_ptr<stream> s = ...; return f(s).then([s](future<int> op) { s->close(); }); }     ,   ,          .       resumable : n3722 .        : future<int> f(stream str) resumable { shared_ptr<vector<char>> buf = ...; int count = await str.read(512, buf); return count + 11; } future<void> g() resumable { stream s = ...; int pls11 = await f(s); s.close(); }   resumable ,    ,    ,       .     await –     ( <- )  do   . ,   str.read  f    future,      await  int ,       . 
 
      ?  ,    ,      :           resumable ,  ,   Fibers  Windows  boost::coroutine .    ,     .     resumable   -     ,    await . ,   await    then       ,    await .    resumable     std::future ,          then  get .         C++,        ,    ,  ,   .            std::future . 
  ,    resumable       .        ,     resumable     . 

Monad. , .
template<typename A, typename B> Monad<B> operator>>=(Monad<A> ma, function<Monad<B> (A)> f) { ... // } ma, f f.

template<typename A, typename B> Monad<B> operator>>(Monad<A> ma, Monad<B> mb) { return Ma >>= [=](A){ return mb; }; } >>= , . ( m >> k = m >>= \_ -> k ), Haskell C++.

template<typename A> Monad <A> mreturn(A a) { ... // } return C++, mreturn. , a .
fail , .

, C++, - . - Maybe , ., std::future . C++11. future T , . , , - , , , , . future get .
template<class T> class future { public: ... T get(); // get ... };
C++11 – std::async . , std::future . : future<int> result = async(f); // - f int a = result.get(); // f .
mreturn >>= std::future #include <future> using namespace std; template<typename A> future<A> mreturn(const A& a) { return async([=]{ return a; }); } , future , . , .

template<typename A, typename B> future<B> operator>>=(future<A>& ma, const function<future<B> (A)>& f) { return async([&] () -> B { return f(ma.get()).get(); }); } , , ma, f, f.

, . 3 , : Left identity : return a >>= f == fa Right identity: m >>= return == m Associativity: (m >>= f) >>= g == m >>= (\x -> fx >>= g)
C++, :
(mreturn(a) >>= f) == f(a) , :
async([&] () -> B { return f(mreturn(a).get()).get(); }) == f(a) , mreturn(a).get() , . a std::future , . , :
async([&] () -> B { return f(a).get(); }) == f(a) , , f , . , f , ( ).

: m >>= mreturn == m , :
async([&] () -> B { return mreturn(m.get()).get(); }) == m mreturn(x).get() , :
async([&] () -> B { return m.get(); }) == m , m. , m.

: (m >>= f) >>= g == m >>= (\x -> fx >>= g) , , . m f, , m. g, f. f g m.

. - : function<future<int> (int)> f = [](int a){ cout << a << '\n'; return mreturn(a + 6); }; int a = (mreturn(5) >>= f).get(); cout << a; , 5 11.

C++11 mreturn >>=. : n3721
mreturn make_ready_future .
>>= , std::future then . , A , future. , , future , then , .
unwrap future<future> future. join Control.Monad .

then : future<int> f(shared_ptr<stream> str) { shared_ptr<vector<char>> buf = ...; return str->read(512, buf).then([](future<int> op) { return op.get() + 11; }); } future<void> g() { shared_ptr<stream> s = ...; return f(s).then([s](future<int> op) { s->close(); }); } , , . resumable : n3722 . : future<int> f(stream str) resumable { shared_ptr<vector<char>> buf = ...; int count = await str.read(512, buf); return count + 11; } future<void> g() resumable { stream s = ...; int pls11 = await f(s); s.close(); } resumable , , , . await – ( <- ) do . , str.read f future, await int , .

? , , : resumable , , Fibers Windows boost::coroutine . , . resumable - , await . , await then , await . resumable std::future , then get . C++, , , , . std::future .
, resumable . , resumable .

 Monad. ,     . 
 template<typename A, typename B> Monad<B> operator>>=(Monad<A> ma, function<Monad<B> (A)> f) { ... //     }       ma,    f    f. 
 
 template<typename A, typename B> Monad<B> operator>>(Monad<A> ma, Monad<B> mb) { return Ma >>= [=](A){ return mb; }; }     >>= ,        .       ( m >> k = m >>= \_ -> k ),     Haskell  C++. 
 
 template<typename A> Monad <A> mreturn(A a) { ... //     }  return    C++,      mreturn.     ,     a       . 
  fail    ,        . 
 
 ,        C++,    -        .         - Maybe ,   .,     std::future .      C++11.   future       T ,     .   , ,   -   ,      ,   ,  ,      .    future      get . 
 template<class T> class future { public: ... T get(); //  get         ... }; 
   C++11    – std::async .      ,           std::future .       : future<int> result = async(f); //  -      f int a = result.get(); //    f    . 
        mreturn  >>=   std::future #include <future> using namespace std; template<typename A> future<A> mreturn(const A& a) { return async([=]{ return a; }); }  ,       future      ,   .     ,    . 
 
 template<typename A, typename B> future<B> operator>>=(future<A>& ma, const function<future<B> (A)>& f) { return async([&] () -> B { return f(ma.get()).get(); }); }   ,    ,         ma,       f,         f. 
 
  ,      .    3 ,     : Left identity : return a >>= f == fa Right identity: m >>= return == m Associativity: (m >>= f) >>= g == m >>= (\x -> fx >>= g) 
     C++, : 
 (mreturn(a) >>= f) == f(a)   , : 
 async([&] () -> B { return f(mreturn(a).get()).get(); }) == f(a) ,  mreturn(a).get()   ,   .     a  std::future ,     . , : 
 async([&] () -> B { return f(a).get(); }) == f(a)  ,  ,     f ,        .   ,   f  ,      (   ). 
 
  : m >>= mreturn == m   , : 
 async([&] () -> B { return mreturn(m.get()).get(); }) == m      mreturn(x).get() , : 
 async([&] () -> B { return m.get(); }) == m  ,     m.    ,        m. 
 
  : (m >>= f) >>= g == m >>= (\x -> fx >>= g)       ,   ,   .      m   f,   ,      m.       g,     f.     f  g             m. 
 
    .    -     : function<future<int> (int)> f = [](int a){ cout << a << '\n'; return mreturn(a + 6); }; int a = (mreturn(5) >>= f).get(); cout << a;   ,    5  11. 
 
  C++11      mreturn  >>=.      : n3721 
  mreturn  make_ready_future . 
  >>= ,    std::future   then .     ,       A ,   future.     ,        ,   future    ,   then ,   . 
     unwrap      future<future>  future.   join  Control.Monad  . 
 
  then     : future<int> f(shared_ptr<stream> str) { shared_ptr<vector<char>> buf = ...; return str->read(512, buf).then([](future<int> op) { return op.get() + 11; }); } future<void> g() { shared_ptr<stream> s = ...; return f(s).then([s](future<int> op) { s->close(); }); }     ,   ,          .       resumable : n3722 .        : future<int> f(stream str) resumable { shared_ptr<vector<char>> buf = ...; int count = await str.read(512, buf); return count + 11; } future<void> g() resumable { stream s = ...; int pls11 = await f(s); s.close(); }   resumable ,    ,    ,       .     await –     ( <- )  do   . ,   str.read  f    future,      await  int ,       . 
 
      ?  ,    ,      :           resumable ,  ,   Fibers  Windows  boost::coroutine .    ,     .     resumable   -     ,    await . ,   await    then       ,    await .    resumable     std::future ,          then  get .         C++,        ,    ,  ,   .            std::future . 
  ,    resumable       .        ,     resumable     . 

Monad. , .
template<typename A, typename B> Monad<B> operator>>=(Monad<A> ma, function<Monad<B> (A)> f) { ... // } ma, f f.

template<typename A, typename B> Monad<B> operator>>(Monad<A> ma, Monad<B> mb) { return Ma >>= [=](A){ return mb; }; } >>= , . ( m >> k = m >>= \_ -> k ), Haskell C++.

template<typename A> Monad <A> mreturn(A a) { ... // } return C++, mreturn. , a .
fail , .

, C++, - . - Maybe , ., std::future . C++11. future T , . , , - , , , , . future get .
template<class T> class future { public: ... T get(); // get ... };
C++11 – std::async . , std::future . : future<int> result = async(f); // - f int a = result.get(); // f .
mreturn >>= std::future #include <future> using namespace std; template<typename A> future<A> mreturn(const A& a) { return async([=]{ return a; }); } , future , . , .

template<typename A, typename B> future<B> operator>>=(future<A>& ma, const function<future<B> (A)>& f) { return async([&] () -> B { return f(ma.get()).get(); }); } , , ma, f, f.

, . 3 , : Left identity : return a >>= f == fa Right identity: m >>= return == m Associativity: (m >>= f) >>= g == m >>= (\x -> fx >>= g)
C++, :
(mreturn(a) >>= f) == f(a) , :
async([&] () -> B { return f(mreturn(a).get()).get(); }) == f(a) , mreturn(a).get() , . a std::future , . , :
async([&] () -> B { return f(a).get(); }) == f(a) , , f , . , f , ( ).

: m >>= mreturn == m , :
async([&] () -> B { return mreturn(m.get()).get(); }) == m mreturn(x).get() , :
async([&] () -> B { return m.get(); }) == m , m. , m.

: (m >>= f) >>= g == m >>= (\x -> fx >>= g) , , . m f, , m. g, f. f g m.

. - : function<future<int> (int)> f = [](int a){ cout << a << '\n'; return mreturn(a + 6); }; int a = (mreturn(5) >>= f).get(); cout << a; , 5 11.

C++11 mreturn >>=. : n3721
mreturn make_ready_future .
>>= , std::future then . , A , future. , , future , then , .
unwrap future<future> future. join Control.Monad .

then : future<int> f(shared_ptr<stream> str) { shared_ptr<vector<char>> buf = ...; return str->read(512, buf).then([](future<int> op) { return op.get() + 11; }); } future<void> g() { shared_ptr<stream> s = ...; return f(s).then([s](future<int> op) { s->close(); }); } , , . resumable : n3722 . : future<int> f(stream str) resumable { shared_ptr<vector<char>> buf = ...; int count = await str.read(512, buf); return count + 11; } future<void> g() resumable { stream s = ...; int pls11 = await f(s); s.close(); } resumable , , , . await – ( <- ) do . , str.read f future, await int , .

? , , : resumable , , Fibers Windows boost::coroutine . , . resumable - , await . , await then , await . resumable std::future , then get . C++, , , , . std::future .
, resumable . , resumable .

 Monad. ,     . 
 template<typename A, typename B> Monad<B> operator>>=(Monad<A> ma, function<Monad<B> (A)> f) { ... //     }       ma,    f    f. 
 
 template<typename A, typename B> Monad<B> operator>>(Monad<A> ma, Monad<B> mb) { return Ma >>= [=](A){ return mb; }; }     >>= ,        .       ( m >> k = m >>= \_ -> k ),     Haskell  C++. 
 
 template<typename A> Monad <A> mreturn(A a) { ... //     }  return    C++,      mreturn.     ,     a       . 
  fail    ,        . 
 
 ,        C++,    -        .         - Maybe ,   .,     std::future .      C++11.   future       T ,     .   , ,   -   ,      ,   ,  ,      .    future      get . 
 template<class T> class future { public: ... T get(); //  get         ... }; 
   C++11    – std::async .      ,           std::future .       : future<int> result = async(f); //  -      f int a = result.get(); //    f    . 
        mreturn  >>=   std::future #include <future> using namespace std; template<typename A> future<A> mreturn(const A& a) { return async([=]{ return a; }); }  ,       future      ,   .     ,    . 
 
 template<typename A, typename B> future<B> operator>>=(future<A>& ma, const function<future<B> (A)>& f) { return async([&] () -> B { return f(ma.get()).get(); }); }   ,    ,         ma,       f,         f. 
 
  ,      .    3 ,     : Left identity : return a >>= f == fa Right identity: m >>= return == m Associativity: (m >>= f) >>= g == m >>= (\x -> fx >>= g) 
     C++, : 
 (mreturn(a) >>= f) == f(a)   , : 
 async([&] () -> B { return f(mreturn(a).get()).get(); }) == f(a) ,  mreturn(a).get()   ,   .     a  std::future ,     . , : 
 async([&] () -> B { return f(a).get(); }) == f(a)  ,  ,     f ,        .   ,   f  ,      (   ). 
 
  : m >>= mreturn == m   , : 
 async([&] () -> B { return mreturn(m.get()).get(); }) == m      mreturn(x).get() , : 
 async([&] () -> B { return m.get(); }) == m  ,     m.    ,        m. 
 
  : (m >>= f) >>= g == m >>= (\x -> fx >>= g)       ,   ,   .      m   f,   ,      m.       g,     f.     f  g             m. 
 
    .    -     : function<future<int> (int)> f = [](int a){ cout << a << '\n'; return mreturn(a + 6); }; int a = (mreturn(5) >>= f).get(); cout << a;   ,    5  11. 
 
  C++11      mreturn  >>=.      : n3721 
  mreturn  make_ready_future . 
  >>= ,    std::future   then .     ,       A ,   future.     ,        ,   future    ,   then ,   . 
     unwrap      future<future>  future.   join  Control.Monad  . 
 
  then     : future<int> f(shared_ptr<stream> str) { shared_ptr<vector<char>> buf = ...; return str->read(512, buf).then([](future<int> op) { return op.get() + 11; }); } future<void> g() { shared_ptr<stream> s = ...; return f(s).then([s](future<int> op) { s->close(); }); }     ,   ,          .       resumable : n3722 .        : future<int> f(stream str) resumable { shared_ptr<vector<char>> buf = ...; int count = await str.read(512, buf); return count + 11; } future<void> g() resumable { stream s = ...; int pls11 = await f(s); s.close(); }   resumable ,    ,    ,       .     await –     ( <- )  do   . ,   str.read  f    future,      await  int ,       . 
 
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template<typename A, typename B> Monad<B> operator>>=(Monad<A> ma, function<Monad<B> (A)> f) { ... // } ma, f f.

template<typename A, typename B> Monad<B> operator>>(Monad<A> ma, Monad<B> mb) { return Ma >>= [=](A){ return mb; }; } >>= , . ( m >> k = m >>= \_ -> k ), Haskell C++.

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mreturn >>= std::future #include <future> using namespace std; template<typename A> future<A> mreturn(const A& a) { return async([=]{ return a; }); } , future , . , .

template<typename A, typename B> future<B> operator>>=(future<A>& ma, const function<future<B> (A)>& f) { return async([&] () -> B { return f(ma.get()).get(); }); } , , ma, f, f.

, . 3 , : Left identity : return a >>= f == fa Right identity: m >>= return == m Associativity: (m >>= f) >>= g == m >>= (\x -> fx >>= g)
C++, :
(mreturn(a) >>= f) == f(a) , :
async([&] () -> B { return f(mreturn(a).get()).get(); }) == f(a) , mreturn(a).get() , . a std::future , . , :
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: m >>= mreturn == m , :
async([&] () -> B { return mreturn(m.get()).get(); }) == m mreturn(x).get() , :
async([&] () -> B { return m.get(); }) == m , m. , m.

: (m >>= f) >>= g == m >>= (\x -> fx >>= g) , , . m f, , m. g, f. f g m.

. - : function<future<int> (int)> f = [](int a){ cout << a << '\n'; return mreturn(a + 6); }; int a = (mreturn(5) >>= f).get(); cout << a; , 5 11.

C++11 mreturn >>=. : n3721
mreturn make_ready_future .
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unwrap future<future> future. join Control.Monad .

then : future<int> f(shared_ptr<stream> str) { shared_ptr<vector<char>> buf = ...; return str->read(512, buf).then([](future<int> op) { return op.get() + 11; }); } future<void> g() { shared_ptr<stream> s = ...; return f(s).then([s](future<int> op) { s->close(); }); } , , . resumable : n3722 . : future<int> f(stream str) resumable { shared_ptr<vector<char>> buf = ...; int count = await str.read(512, buf); return count + 11; } future<void> g() resumable { stream s = ...; int pls11 = await f(s); s.close(); } resumable , , , . await – ( <- ) do . , str.read f future, await int , .

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