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.

The version range -any. That is, a version range containing all versions.

 withinRange v anyVersion = True

The empty version range, that is a version range containing no versions.

This can be constructed using any unsatisfiable version range expression, for example > 1 && < 1.

 withinRange v anyVersion = False

The version range == v

 withinRange v' (thisVersion v) = v' == v

The version range || v

 withinRange v' (notThisVersion v) = v' /= v

The version range > v

 withinRange v' (laterVersion v) = v' > v

The version range < v

 withinRange v' (earlierVersion v) = v' < v

The version range >= v

 withinRange v' (orLaterVersion v) = v' >= v

The version range <= v

 withinRange v' (orEarlierVersion v) = v' <= v

The version range vr1 || vr2

   withinRange v' (unionVersionRanges vr1 vr2)
 = withinRange v' vr1 || withinRange v' vr2

The version range vr1 && vr2

   withinRange v' (intersectVersionRanges vr1 vr2)
 = withinRange v' vr1 && withinRange v' vr2

The version range == v.*.

For example, for version 1.2, the version range == 1.2.* is the same as >= 1.2 && < 1.3

 withinRange v' (laterVersion v) = v' >= v && v' < upper v
   where
     upper (Version lower t) = Version (init lower ++ [last lower + 1]) t

The version range >= v1 && <= v2.

In practice this is not very useful because we normally use inclusive lower bounds and exclusive upper bounds.

 withinRange v' (laterVersion v) = v' > v

Does this version fall within the given range?

This is the evaluation function for the VersionRange type.

Does this VersionRange place any restriction on the Version or is it in fact equivalent to AnyVersion.

Note this is a semantic check, not simply a syntactic check. So for example the following is True (for all v).

 isAnyVersion (EarlierVersion v `UnionVersionRanges` orLaterVersion v)

This is the converse of isAnyVersion. It check if the version range is empty, if there is no possible version that satisfies the version range.

For example this is True (for all v):

 isNoVersion (EarlierVersion v `IntersectVersionRanges` LaterVersion v)

Is this version range in fact just a specific version?

For example the version range ">= 3 && <= 3" contains only the version 3.

Simplify a VersionRange expression. For non-empty version ranges this produces a canonical form. Empty or inconsistent version ranges are left as-is because that provides more information.

If you need a canonical form use fromVersionIntervals . toVersionIntervals

It satisfies the following properties:

 withinRange v (simplifyVersionRange r) = withinRange v r

     withinRange v r = withinRange v r'
 ==> simplifyVersionRange r = simplifyVersionRange r'
  || isNoVersion r
  || isNoVersion r'

Fold over the basic syntactic structure of a VersionRange.

This provides a syntacic view of the expression defining the version range. The syntactic sugar ">= v", "<= v" and "== v.*" is presented in terms of the other basic syntax.

For a semantic view use asVersionIntervals.

An extended variant of foldVersionRange that also provides a view of in which the syntactic sugar ">= v", "<= v" and "== v.*" is presented explicitly rather than in terms of the other basic syntax.

View a VersionRange as a union of intervals.

This provides a canonical view of the semantics of a VersionRange as opposed to the syntax of the expression used to define it. For the syntactic view use foldVersionRange.

Each interval is non-empty. The sequence is in increasing order and no intervals overlap or touch. Therefore only the first and last can be unbounded. The sequence can be empty if the range is empty (e.g. a range expression like && 2).

Other checks are trivial to implement using this view. For example:

 isNoVersion vr | [] <- asVersionIntervals vr = True
                | otherwise                   = False

 isSpecificVersion vr
    | [(LowerBound v  InclusiveBound
       ,UpperBound v' InclusiveBound)] <- asVersionIntervals vr
    , v == v'   = Just v
    | otherwise = Nothing

A complementary representation of a VersionRange. Instead of a boolean version predicate it uses an increasing sequence of non-overlapping, non-empty intervals.

The key point is that this representation gives a canonical representation for the semantics of VersionRanges. This makes it easier to check things like whether a version range is empty, covers all versions, or requires a certain minimum or maximum version. It also makes it easy to check equality or containment. It also makes it easier to identify 'simple' version predicates for translation into foreign packaging systems that do not support complex version range expressions.

Convert a VersionRange to a sequence of version intervals.

Convert a VersionIntervals value back into a VersionRange expression representing the version intervals.

Test if a version falls within the version intervals.

It exists mostly for completeness and testing. It satisfies the following properties:

 withinIntervals v (toVersionIntervals vr) = withinRange v vr
 withinIntervals v ivs = withinRange v (fromVersionIntervals ivs)

Inspect the list of version intervals.

Directly construct a VersionIntervals from a list of intervals.

Each interval must be non-empty. The sequence must be in increasing order and no invervals may overlap or touch. If any of these conditions are not satisfied the function returns Nothing.