project1st

Category: functors		Component type: type

Description

Project1st is a functors that takes two arguments and returns its first argument; the second argument is unused. It is essentially a generalization of identity to the case of a BinaryFunction.

Example

int main()
{
  Vector<int> v1(10, 137);
  Vector<char*> v2(10, (char*) 0);
  Vector<int> result(10);

  transform(v1.begin(), v1.end(), v2.begin(), result.begin(),
            project1st<int, char*>());
  assert(equal(v1.begin(), v1.end(), result.begin()));
}           

Definition

Defined in the standard header functional, and in the nonstandard backward-compatibility header function.h.
This function object is an SGI extension; it is not part of the C++ standard.

Template parameters

Parameter	Description	Default
Arg1	project1st's first argument type, and its result type.
Arg2	project1st's second argument type.

Model of

AdaptableBinaryFunction

Type requirements

None.

Public base classes

binary_function<Arg1, Arg2, Arg1>

Members

Member	Where defined	Description
first_argument_type	AdaptableBinaryFunction	The type of project1st's first argument: Arg1
second_argument_type	AdaptableBinaryFunction	The type of project1st's second argument: Arg2
result_type	AdaptableBinaryFunction	The type of the result: Arg1.
Arg1 operator()(const Arg1& x, const Arg2&) const	AdaptableBinaryFunction	Function call. The return value is x.

New members

All of project1st's members are defined in the AdaptableBinaryFunction requirements. project1st does not introduce any new members.

Notes

See also

functors, identity, project2nd, select1st, select2nd