libstdc++

Classes  
class  std::binder1st< _Operation > 
class  std::binder2nd< _Operation > 
Functions  
template<typename _Operation , typename _Tp >  
binder1st< _Operation >  std::bind1st (const _Operation &__fn, const _Tp &__x) 
template<typename _Operation , typename _Tp >  
binder2nd< _Operation >  std::bind2nd (const _Operation &__fn, const _Tp &__x) 
Binders turn functions/functors with two arguments into functors with a single argument, storing an argument to be applied later. For example, a variable B
of type binder1st
is constructed from a functor f
and an argument x
. Later, B's operator()
is called with a single argument y
. The return value is the value of f(x,y)
. B
can be called with various arguments (y1, y2, ...) and will in turn call f(x,y1)
, f(x,y2)
, ...
The function bind1st
is provided to save some typing. It takes the function and an argument as parameters, and returns an instance of binder1st
.
The type binder2nd
and its creator function bind2nd
do the same thing, but the stored argument is passed as the second parameter instead of the first, e.g., bind2nd
(std::minus<float>(),1.3) will create a functor whose operator()
accepts a floatingpoint number, subtracts 1.3 from it, and returns the result. (If bind1st
had been used, the functor would perform 1.3  x instead.
Creatorwrapper functions like bind1st
are intended to be used in calling algorithms. Their return values will be temporary objects. (The goal is to not require you to type names like std::binder1st<std::plus<int>>
for declaring a variable to hold the return value from bind1st(std::plus<int>(),5)
.
These become more useful when combined with the composition functions.
These functions are deprecated in C++11 and can be replaced by std::bind
(or std::tr1::bind
) which is more powerful and flexible, supporting functions with any number of arguments. Uses of bind1st
can be replaced by std::bind(f, x, std::placeholders::_1)
and bind2nd
by std::bind(f, std::placeholders::_1, x)
.

inline 
One of the binder functors.

inline 
One of the binder functors.