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# ===========================================================================
# https://www.gnu.org/software/autoconf-archive/ax_cxx_have_hash.html
# ===========================================================================
#
# SYNOPSIS
#
# AX_CXX_HAVE_HASH()
#
# DESCRIPTION
#
# This macro checks if std::hash, added in C++11, is defined in the
# <functional> header.
#
# If it is, define the ax_cv_cxx_have_hash environment variable to "yes"
# and define HAVE_CXX_HASH.
#
# LICENSE
#
# Copyright (c) 2014 Enrico M. Crisostomo <enrico.m.crisostomo@gmail.com>
#
# Copying and distribution of this file, with or without modification, are
# permitted in any medium without royalty provided the copyright notice
# and this notice are preserved. This file is offered as-is, without any
# warranty.
#serial 3
AC_DEFUN([AX_CXX_HAVE_HASH],
[AC_CACHE_CHECK(
[for std::hash in functional],
ax_cv_cxx_have_hash,
[dnl
AC_LANG_PUSH([C++])
AC_COMPILE_IFELSE([AC_LANG_PROGRAM(
[
[#include <functional>]
[#include <string>]
[using std::hash;]
],
[]
)],
[ax_cv_cxx_have_hash=yes],
[ax_cv_cxx_have_hash=no]
)
AC_LANG_POP([C++])])
if test x"$ax_cv_cxx_have_hash" = "xyes"
then
AC_DEFINE(HAVE_CXX_HASH,
1,
[Define if functional defines the std::hash class.])
fi
])
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