Standard Template Library Programmer's Guide

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
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.

See also

The function object overview, Adaptable Binary Predicate, not_equal_to, greater, less, greater_equal, less_equal

not_equal_to<T>

Category: functors

Component type: type

Description

Not_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 not_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

Finds the first nonzero element in a list.

list<int> L;
…
list<int>::iterator first_nonzero = find_if(L.begin(), L.end(), bind2nd(not_equal_to<int> (), 0));
assert(first_nonzero == L.end() || *first_nonzero != 0);

Definition

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

Template parameters