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Standard Template Library Programmer's Guide
(document number: 007-3426-004 / published: 1999-05-21) table of contents | additional info | download
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project1st<Arg1, Arg2>


Category: functors	Component type: type

Description

Project1st is a function object 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 Binary Function.

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

Adaptable Binary Function

Type requirements

None.

Public base classes

binary_function<Arg1, Arg2, Arg1>

Members

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

New members

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