##### http://autoconf-archive.cryp.to/ax_expand_prefix.html
#
# SYNOPSIS
#
#   AX_EXPAND_PREFIX
#
# DESCRIPTION
#
#   When $prefix and $exec_prefix are still set to NONE then set them
#   to the usual default values - being based on $ac_default_prefix. -
#   this macro can be AC_REQUIREd by other macros that need to compute
#   values for installation directories. It has been observed that it
#   was done wrong over and over again, so this is a bit more safe to
#   do.
#
#   remember - setting exec_prefix='${prefix}' needs you interpolate
#   directories multiple times, it is not sufficient to just say
#   MYVAR="${datadir}/putter" but you do have to run `eval` a few
#   times, sth. like MYVAR=`eval "echo \"$MYVAR\""` done atleast two
#   times.
#
#   The implementation of this macro simply picks up the lines that
#   would be run at the start of AC_OUTPUT anyway to set the
#   prefix/exec_prefix defaults. Between AC_INIT and the first command
#   to AC_REQUIRE this macro you can set the two variables to something
#   explicit instead. Probably, any command to compute installation
#   directories should be run _after_ AM_INIT_AUTOMAKE
#
# LAST MODIFICATION
#
#   2006-10-13
#
# COPYLEFT
#
#   Copyright (c) 2006 Guido U. Draheim <guidod@gmx.de>
#
#   This program is free software; you can redistribute it and/or
#   modify it under the terms of the GNU General Public License as
#   published by the Free Software Foundation; either version 2 of the
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#
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#   WITHOUT ANY WARRANTY; without even the implied warranty of
#   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
#   General Public License for more details.
#
#   You should have received a copy of the GNU General Public License
#   along with this program; if not, write to the Free Software
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#   02111-1307, USA.
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AC_DEFUN([AX_EXPAND_PREFIX],[dnl
  # The prefix default can be set in configure.ac (otherwise it is /usr/local)
  test "x$prefix" = xNONE && prefix=$ac_default_prefix
  # Let make expand exec_prefix. Allows to override the makevar 'prefix' later
  test "x$exec_prefix" = xNONE && exec_prefix='${prefix}'
])