.TH "std::__is_fast_hash< _Hash >" 3cxx "libstdc++" \" -*- nroff -*-
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.SH NAME
std::__is_fast_hash< _Hash >
.SH SYNOPSIS
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.PP
.PP
\fC#include <functional>\fP
.PP
Inherits \fBstd::integral_constant< _Tp, __v >\fP\&.
.SS "Public Types"

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.ti -1c
.RI "\fBtypedef\fP \fBintegral_constant\fP< _Tp, \fB__v\fP > \fBtype\fP"
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.ti -1c
.RI "\fBtypedef\fP _Tp \fBvalue_type\fP"
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.SS "Public Member Functions"

.in +1c
.ti -1c
.RI "constexpr \fBoperator value_type\fP () const noexcept"
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.ti -1c
.RI "constexpr value_type \fBoperator()\fP () const noexcept"
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.in -1c
.SS "Static Public Attributes"

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.ti -1c
.RI "\fBstatic\fP constexpr _Tp \fBvalue\fP"
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.in -1c
.SH "Detailed Description"
.PP 

.SS "template<\fBtypename\fP \fB_Hash\fP>
.br
struct std::__is_fast_hash< _Hash >"Hint about performance of hash functions\&.
.PP
If a given hash function object is not fast, the hash-based containers will cache the hash code\&. The default behavior is to consider that hashers are fast unless specified otherwise\&.
.PP
Users can specialize this for their own hash functions in order to force caching of hash codes in unordered containers\&. Specializing this trait affects the ABI of the unordered containers, so use it carefully\&. 

.SH "Author"
.PP 
Generated automatically by Doxygen for libstdc++ from the source code\&.