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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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equal_to<T>


Category: functors	Component type: type

Description

Equal_to<T> is a function object. Specifically, it is an Adaptable Binary Predicate, which means it is a function object that tests the truth or falsehood of some condition. If f is an object of class equal_to<T> and x and y are objects of class T, then f(x,y) returns true if x == y and false otherwise.

Example

Rearrange a vector such that all of the elements that are equal to zero precede all nonzero elements.

vector<int> V;
...
partition(V.begin(), V.end(), bind2nd(equal_to<int>(), 0));

Definition

Defined in the standard header functional, and in the nonstandard backward-compatibility header function.h.

Template parameters

Parameter	Description	Default
`T`	The type of `equal_to`'s arguments.

Model of

Adaptable Binary Predicate, DefaultConstructible

Type requirements

T is EqualityComparable.

Public base classes

binary_function<T, T, bool>.

Members

Member	Where defined	Description
`first_argument_type`	Adaptable Binary Predicate	The type of the first argument: `T`
`second_argument_type`	Adaptable Binary Predicate	The type of the second argument: `T`
`result_type`	Adaptable Binary Predicate	The type of the result: `bool`
`equal_to()`	DefaultConstructible	The default constructor.
`bool operator()(const T& x, const T& y)`	Binary Function	Function call operator. The return value is `x == y`.

New members

All of equal_to's members are defined in the Adaptable Binary Predicate and DefaultConstructible requirements. Equal_to does not introduce any new members.