Implementing Haskell's Maybe Monad in c++11

Question

I am trying to implement the Maybe monad from Haskell using the lambda functions in C++11 and templates. Here\'s what I have so far

#include
#i         


        

Answer 1

The following works for me: I use decltype to infer the type returned by the lambda:

template    
auto operator>>=(Maybe t, Func f) -> decltype(f(t.data))
{    
  decltype(f(t.data)) return_value;    
  if(t.valid == false)    
  {            
    return_value.valid = false;    
    return return_value;    
  }    
  else    
  {            
    return f(t.data);    
  }                
}

EDIT

For type safety :

template    
struct Maybe    
{    
  T1 data;    
  bool valid;

  static const bool isMaybe = true;
};

template     
auto operator>>=(Maybe t, Func f) -> decltype(f(t.data)) 
{
  typedef decltype(f(t.data)) RT;
  static_assert(RT::isMaybe, "F doesn't return a maybe");
  ...