--- /dev/null
+##### http://autoconf-archive.cryp.to/ax_compare_version.html
+#
+# SYNOPSIS
+#
+# AX_COMPARE_VERSION(VERSION_A, OP, VERSION_B, [ACTION-IF-TRUE], [ACTION-IF-FALSE])
+#
+# DESCRIPTION
+#
+# This macro compares two version strings. It is used heavily in the
+# macro _AX_PATH_BDB for library checking. Due to the various number
+# of minor-version numbers that can exist, and the fact that string
+# comparisons are not compatible with numeric comparisons, this is
+# not necessarily trivial to do in a autoconf script. This macro
+# makes doing these comparisons easy.
+#
+# The six basic comparisons are available, as well as checking
+# equality limited to a certain number of minor-version levels.
+#
+# The operator OP determines what type of comparison to do, and can
+# be one of:
+#
+# eq - equal (test A == B)
+# ne - not equal (test A != B)
+# le - less than or equal (test A <= B)
+# ge - greater than or equal (test A >= B)
+# lt - less than (test A < B)
+# gt - greater than (test A > B)
+#
+# Additionally, the eq and ne operator can have a number after it to
+# limit the test to that number of minor versions.
+#
+# eq0 - equal up to the length of the shorter version
+# ne0 - not equal up to the length of the shorter version
+# eqN - equal up to N sub-version levels
+# neN - not equal up to N sub-version levels
+#
+# When the condition is true, shell commands ACTION-IF-TRUE are run,
+# otherwise shell commands ACTION-IF-FALSE are run. The environment
+# variable 'ax_compare_version' is always set to either 'true' or
+# 'false' as well.
+#
+# Examples:
+#
+# AX_COMPARE_VERSION([3.15.7],[lt],[3.15.8])
+# AX_COMPARE_VERSION([3.15],[lt],[3.15.8])
+#
+# would both be true.
+#
+# AX_COMPARE_VERSION([3.15.7],[eq],[3.15.8])
+# AX_COMPARE_VERSION([3.15],[gt],[3.15.8])
+#
+# would both be false.
+#
+# AX_COMPARE_VERSION([3.15.7],[eq2],[3.15.8])
+#
+# would be true because it is only comparing two minor versions.
+#
+# AX_COMPARE_VERSION([3.15.7],[eq0],[3.15])
+#
+# would be true because it is only comparing the lesser number of
+# minor versions of the two values.
+#
+# Note: The characters that separate the version numbers do not
+# matter. An empty string is the same as version 0. OP is evaluated
+# by autoconf, not configure, so must be a string, not a variable.
+#
+# The author would like to acknowledge Guido Draheim whose advice
+# about the m4_case and m4_ifvaln functions make this macro only
+# include the portions necessary to perform the specific comparison
+# specified by the OP argument in the final configure script.
+#
+# LAST MODIFICATION
+#
+# 2004-03-01
+#
+# COPYLEFT
+#
+# Copyright (c) 2004 Tim Toolan <toolan@ele.uri.edu>
+#
+# 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
+# License, or (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful, but
+# 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
+# Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA
+# 02111-1307, USA.
+#
+# As a special exception, the respective Autoconf Macro's copyright
+# owner gives unlimited permission to copy, distribute and modify the
+# configure scripts that are the output of Autoconf when processing
+# the Macro. You need not follow the terms of the GNU General Public
+# License when using or distributing such scripts, even though
+# portions of the text of the Macro appear in them. The GNU General
+# Public License (GPL) does govern all other use of the material that
+# constitutes the Autoconf Macro.
+#
+# This special exception to the GPL applies to versions of the
+# Autoconf Macro released by the Autoconf Macro Archive. When you
+# make and distribute a modified version of the Autoconf Macro, you
+# may extend this special exception to the GPL to apply to your
+# modified version as well.
+
+dnl #########################################################################
+AC_DEFUN([AX_COMPARE_VERSION], [
+ # Used to indicate true or false condition
+ ax_compare_version=false
+
+ # Convert the two version strings to be compared into a format that
+ # allows a simple string comparison. The end result is that a version
+ # string of the form 1.12.5-r617 will be converted to the form
+ # 0001001200050617. In other words, each number is zero padded to four
+ # digits, and non digits are removed.
+ AS_VAR_PUSHDEF([A],[ax_compare_version_A])
+ A=`echo "$1" | sed -e 's/\([[0-9]]*\)/Z\1Z/g' \
+ -e 's/Z\([[0-9]]\)Z/Z0\1Z/g' \
+ -e 's/Z\([[0-9]][[0-9]]\)Z/Z0\1Z/g' \
+ -e 's/Z\([[0-9]][[0-9]][[0-9]]\)Z/Z0\1Z/g' \
+ -e 's/[[^0-9]]//g'`
+
+ AS_VAR_PUSHDEF([B],[ax_compare_version_B])
+ B=`echo "$3" | sed -e 's/\([[0-9]]*\)/Z\1Z/g' \
+ -e 's/Z\([[0-9]]\)Z/Z0\1Z/g' \
+ -e 's/Z\([[0-9]][[0-9]]\)Z/Z0\1Z/g' \
+ -e 's/Z\([[0-9]][[0-9]][[0-9]]\)Z/Z0\1Z/g' \
+ -e 's/[[^0-9]]//g'`
+
+ dnl # In the case of le, ge, lt, and gt, the strings are sorted as necessary
+ dnl # then the first line is used to determine if the condition is true.
+ dnl # The sed right after the echo is to remove any indented white space.
+ m4_case(m4_tolower($2),
+ [lt],[
+ ax_compare_version=`echo "x$A
+x$B" | sed 's/^ *//' | sort -r | sed "s/x${A}/false/;s/x${B}/true/;1q"`
+ ],
+ [gt],[
+ ax_compare_version=`echo "x$A
+x$B" | sed 's/^ *//' | sort | sed "s/x${A}/false/;s/x${B}/true/;1q"`
+ ],
+ [le],[
+ ax_compare_version=`echo "x$A
+x$B" | sed 's/^ *//' | sort | sed "s/x${A}/true/;s/x${B}/false/;1q"`
+ ],
+ [ge],[
+ ax_compare_version=`echo "x$A
+x$B" | sed 's/^ *//' | sort -r | sed "s/x${A}/true/;s/x${B}/false/;1q"`
+ ],[
+ dnl Split the operator from the subversion count if present.
+ m4_bmatch(m4_substr($2,2),
+ [0],[
+ # A count of zero means use the length of the shorter version.
+ # Determine the number of characters in A and B.
+ ax_compare_version_len_A=`echo "$A" | awk '{print(length)}'`
+ ax_compare_version_len_B=`echo "$B" | awk '{print(length)}'`
+
+ # Set A to no more than B's length and B to no more than A's length.
+ A=`echo "$A" | sed "s/\(.\{$ax_compare_version_len_B\}\).*/\1/"`
+ B=`echo "$B" | sed "s/\(.\{$ax_compare_version_len_A\}\).*/\1/"`
+ ],
+ [[0-9]+],[
+ # A count greater than zero means use only that many subversions
+ A=`echo "$A" | sed "s/\(\([[0-9]]\{4\}\)\{m4_substr($2,2)\}\).*/\1/"`
+ B=`echo "$B" | sed "s/\(\([[0-9]]\{4\}\)\{m4_substr($2,2)\}\).*/\1/"`
+ ],
+ [.+],[
+ AC_WARNING(
+ [illegal OP numeric parameter: $2])
+ ],[])
+
+ # Pad zeros at end of numbers to make same length.
+ ax_compare_version_tmp_A="$A`echo $B | sed 's/./0/g'`"
+ B="$B`echo $A | sed 's/./0/g'`"
+ A="$ax_compare_version_tmp_A"
+
+ # Check for equality or inequality as necessary.
+ m4_case(m4_tolower(m4_substr($2,0,2)),
+ [eq],[
+ test "x$A" = "x$B" && ax_compare_version=true
+ ],
+ [ne],[
+ test "x$A" != "x$B" && ax_compare_version=true
+ ],[
+ AC_WARNING([illegal OP parameter: $2])
+ ])
+ ])
+
+ AS_VAR_POPDEF([A])dnl
+ AS_VAR_POPDEF([B])dnl
+
+ dnl # Execute ACTION-IF-TRUE / ACTION-IF-FALSE.
+ if test "$ax_compare_version" = "true" ; then
+ m4_ifvaln([$4],[$4],[:])dnl
+ m4_ifvaln([$5],[else $5])dnl
+ fi
+]) dnl AX_COMPARE_VERSION