Re: [Boost-users] correct usage of bind

Subject: Re: [Boost-users] correct usage of bind
From: Roman Perepelitsa (roman.perepelitsa_at_[hidden])
Date: 2009-03-18 04:07:52

2009/3/17 Sandeep Gupta <gupta.sandeep_at_[hidden]>

> Hi,
>  Both the statements below  bind function buildPair.  While the  first
> works the other fails. What could be a  possible fix. Thanks in
> advance.
>
> //---- Function to be used by bind -------------------------
> template<typename X, typename Y>
> std::pair<X, Y> buildPair(X x, Y y)
> {
>  std::pair<X,Y> apair(x,y);
>  return apair;
> }
>
>
> (std::cout<<buildPair(_1,_2).first<<' ')(1,2);     ///--compiles
> fine---------

This one does not bind buildPair, it evaluates buildPair immediately. This
line of code is equivalent to
  (std::cout<<_1<<' ')(1,2);

> (bind(buildPair,_1,_2))(3,5);                  ///-fails------------
>

You should specify template arguments for buildPair.
  (bind(buildPair<int, int>,_1,_2))(3,5);

Roman Perepelitsa.