Standard Template Library Programmer's Guide

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

The requirement for operator!= is that x == y is a valid expression for objects x and y of type T .

The requirement for operator> is that y < x is a valid expression for objects x and y of type T .

The requirement for operator<= is that y < x is a valid expression for objects x and y of type T .

The requirement for operator>= is that x < y is a valid expression for objects x and y of type T .

The precondition for operator!= is that x and y are in the domain of operator== .

The precondition for operator> , operator<= , and operator>= is that x and y are in the domain of operator< .

template

void relations(T x, T y) {

if (x == y) assert(!(x != y));

else assert(x != y);

if (x < y) {

assert(x <= y);

assert(y > x);

assert(y >= x);

} else if (y < x) {

assert(y <= x);

assert(x < y);

assert(x <= y);

} else {

assert(x <= y);

assert(x >= y);

}

}

Equality Comparable, LessThan Comparable

Category: utilities

Component type: type

Pair is a heterogeneous pair: it holds one object of type T1 and one of type T2 . A pair is much like a Container, in that it "owns" its elements. It is not actually a model of Container, though, because it does not support the standard methods (such as iterators) for accessing the elements of a Container.

Functions that need to return two values often return a pair .

pair result = do_a_calculation();

if (result.first) do_something_more(result.second);

else report_error();

Defined in the standard header utility, and in the nonstandard backward-compatibility header pair.h.

Assignable

T1 and T2 must both be models of Assignable. Additional operations have additional requirements. Pair 's default constructor may only be used if both T1 and T2 are DefaultConstructible, operator== may only be used if both T1 and T2 are EqualityComparable, and operator< may only be used if both T1 and T2 are LessThanComparable.

None.

These members are not defined in the Assignable requirements, but are specific to pair .

Assignable, Default Constructible, LessThan Comparable