|Copyright||(c) The University of Glasgow 2004|
|License||BSD-style (see the file libraries/base/LICENSE)|
|Portability||non-portable (local universal quantification in ReadP)|
A general library for representation and manipulation of versions.
Versioning schemes are many and varied, so the version representation provided by this library is intended to be a compromise between complete generality, where almost no common functionality could reasonably be provided, and fixing a particular versioning scheme, which would probably be too restrictive.
So the approach taken here is to provide a representation which
subsumes many of the versioning schemes commonly in use, and we
provide implementations of
Ord and conversion to/from
which will be appropriate for some applications, but not all.
Version represents the version of a software entity.
An instance of
Ord is also provided, which gives lexicographic
ordering on the
versionBranch fields (i.e. 2.1 > 2.0, 1.2.3 > 1.2.2,
etc.). This is expected to be sufficient for many uses, but note that
you may need to use a more specific ordering for your versioning
scheme. For example, some versioning schemes may include pre-releases
which have tags
"pre2", and so on, and these would need to
be taken into account when determining ordering. In some cases, date
ordering may be more appropriate, so the application would have to
date tags in the
versionTags field and compare those.
The bottom line is, don't always assume that
compare and other
operations are the right thing for every
Similarly, concrete representations of versions may differ. One
possible concrete representation is provided (see
parseVersion), but depending on the application a different concrete
representation may be more appropriate.