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 || 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'

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 1 && 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

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)

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.