@node ax_compare_version
@unnumberedsec ax_compare_version

@majorheading Synopsis

@smallexample
AX_COMPARE_VERSION(VERSION_A, OP, VERSION_B, [ACTION-IF-TRUE], [ACTION-IF-FALSE])
@end smallexample

@majorheading Description

This macro compares two version strings. 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:

@smallexample
 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)
@end smallexample

Additionally, the eq and ne operator can have a number after it to limit
the test to that number of minor versions.

@smallexample
 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
@end smallexample

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:

@smallexample
  AX_COMPARE_VERSION([3.15.7],[lt],[3.15.8])
  AX_COMPARE_VERSION([3.15],[lt],[3.15.8])
@end smallexample

would both be true.

@smallexample
  AX_COMPARE_VERSION([3.15.7],[eq],[3.15.8])
  AX_COMPARE_VERSION([3.15],[gt],[3.15.8])
@end smallexample

would both be false.

@smallexample
  AX_COMPARE_VERSION([3.15.7],[eq2],[3.15.8])
@end smallexample

would be true because it is only comparing two minor versions.

@smallexample
  AX_COMPARE_VERSION([3.15.7],[eq0],[3.15])
@end smallexample

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.

@majorheading Source Code

Download the
@uref{http://git.savannah.gnu.org/gitweb/?p=autoconf-archive.git;a=blob_plain;f=m4/ax_compare_version.m4,latest
version of @file{ax_compare_version.m4}} or browse
@uref{http://git.savannah.gnu.org/gitweb/?p=autoconf-archive.git;a=history;f=m4/ax_compare_version.m4,the
macro's revision history}.

@majorheading License

@w{Copyright @copyright{} 2008 Tim Toolan @email{toolan@@ele.uri.edu}}

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.