Standard Template Library Programmer's Guide

case of a Binary Function.

Example

int main() {
 vector<char*> v1(10, (char*) 0);
 vector<int> v2(10, 137);
 vector<int> result(10);
 transform(v1.begin(), v1.end(), v2.begin(), result.begin(), project2nd<char*, int> ());
 assert(equal(v2.begin(), v2.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
Arg1	project2nd's first argument type.
Arg2	project2nd's second argument type, and its result type.

Model of

Adaptable Binary Function

Type requirements

None.

Public base classes

binary_function<Arg1, Arg2, Arg2>

Members

Member	Where defined	Description
first_argument_type	Adaptable Binary Function	The type of project2nd's first argument: Arg1
second_argument_type	Adaptable Binary Function	The type of project2nd's second argument: Arg2
result_type	Adaptable Binary Function	The type of the result: Arg2.
Arg1 operator()(const Arg1&, const Arg2& y) const	Adaptable Binary Function	Function call. The return value is y.

New members

All of project2nd's members are defined in the Adaptable Binary Function requirements. project2nd does not introduce any new members.

See also

Function objects, identity, project1st, select1st, select2nd

select1st<Pair>

Category: functors

Component type: type

Description

Select1st is a function object that takes a single argument, a pair [1], and returns the pair's first element.

Example

Print all of a map's keys.

int main() {
 map<int, double> M;
 M[1] = 0.3;
 M[47] = 0.8;
 M[33] = 0.1;
 transform(M.begin(), M.end(), ostream_iterator<int>(cout, ' '), select1st<map<int, double>::value_type>());
 // The output is 1 33 47.
}

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