base- Basic libraries

Copyright(c) The University of Glasgow 2004
LicenseBSD-style (see the file libraries/base/LICENSE)
Portabilitynon-portable (local universal quantification in ReadP)
Safe HaskellSafe




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 Eq, Ord and conversion to/from String which will be appropriate for some applications, but not all.


The Version type

data Version Source

A Version represents the version of a software entity.

An instance of Eq is provided, which implements exact equality modulo reordering of the tags in the versionTags field.

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 "pre1", "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 look for date tags in the versionTags field and compare those. The bottom line is, don't always assume that compare and other Ord operations are the right thing for every Version.

Similarly, concrete representations of versions may differ. One possible concrete representation is provided (see showVersion and parseVersion), but depending on the application a different concrete representation may be more appropriate.




  • versionBranch :: [Int]

    The numeric branch for this version. This reflects the fact that most software versions are tree-structured; there is a main trunk which is tagged with versions at various points (1,2,3...), and the first branch off the trunk after version 3 is 3.1, the second branch off the trunk after version 3 is 3.2, and so on. The tree can be branched arbitrarily, just by adding more digits.

    We represent the branch as a list of Int, so version 3.2.1 becomes [3,2,1]. Lexicographic ordering (i.e. the default instance of Ord for [Int]) gives the natural ordering of branches.

  • versionTags :: [String]

    Deprecated: See GHC ticket #2496

    A version can be tagged with an arbitrary list of strings. The interpretation of the list of tags is entirely dependent on the entity that this version applies to.


IsList Version Source


Eq Version Source 


(==) :: Version -> Version -> Bool

(/=) :: Version -> Version -> Bool

Data Version Source 


gfoldl :: (forall d b. Data d => c (d -> b) -> d -> c b) -> (forall g. g -> c g) -> Version -> c Version Source

gunfold :: (forall b r. Data b => c (b -> r) -> c r) -> (forall r. r -> c r) -> Constr -> c Version Source

toConstr :: Version -> Constr Source

dataTypeOf :: Version -> DataType Source

dataCast1 :: Typeable (* -> *) t => (forall d. Data d => c (t d)) -> Maybe (c Version) Source

dataCast2 :: Typeable (* -> * -> *) t => (forall d e. (Data d, Data e) => c (t d e)) -> Maybe (c Version) Source

gmapT :: (forall b. Data b => b -> b) -> Version -> Version Source

gmapQl :: (r -> r' -> r) -> r -> (forall d. Data d => d -> r') -> Version -> r Source

gmapQr :: (r' -> r -> r) -> r -> (forall d. Data d => d -> r') -> Version -> r Source

gmapQ :: (forall d. Data d => d -> u) -> Version -> [u] Source

gmapQi :: Int -> (forall d. Data d => d -> u) -> Version -> u Source

gmapM :: Monad m => (forall d. Data d => d -> m d) -> Version -> m Version Source

gmapMp :: MonadPlus m => (forall d. Data d => d -> m d) -> Version -> m Version Source

gmapMo :: MonadPlus m => (forall d. Data d => d -> m d) -> Version -> m Version Source

Ord Version Source 
Read Version Source 
Show Version Source 
type Item Version = Int Source 

A concrete representation of Version

showVersion :: Version -> String Source

Provides one possible concrete representation for Version. For a version with versionBranch = [1,2,3] and versionTags = ["tag1","tag2"], the output will be 1.2.3-tag1-tag2.

parseVersion :: ReadP Version Source

A parser for versions in the format produced by showVersion.

Constructor function

makeVersion :: [Int] -> Version Source

Construct tag-less Version