Hash

A Hash is a function object for which the output depends only on the input and has a very low probability of yielding the same output given different input values.

Requirements

The type T satisfies Hash if.

The type T satisfies FunctionObject, CopyConstructible, Destructible, and

Given.

h, a value of type T or const T, whose argument type is Key
k, a value of type convertible to Key or const Key
u, an lvalue expression of type Key

The following expressions must be valid and have their specified effects.

Expression	Return type	Requirements
`h(k)`	`std::size_t`	the returned value depends only on the value of `k` for the duration of the program (since C++14) All evaluations of `h(k)` executed within a given execution of a program (since C++14) yield the same result for the same value of `k`. The probability of `h(a)==h(b)` for `a!=b` should approach `1.0/std::numeric_limits<std::size_t>::max()`.
`h(u)`	`std::size_t`	`u` is not modified

Standard library

std::hash

Links:

http://en.cppreference.com/w/cpp/concept/Hash

doc_CPP

2016-10-11 09:58:49

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