Darcs.Patch.Permutations

Documentation

removeFL :: (MyEq p, Commute p) => p -> FL p -> Maybe (FL p)

removeFL x xs removes x from xs if x can be commuted to its head. Otherwise it returns Nothing

removeRL :: (MyEq p, Commute p) => p -> RL p -> Maybe (RL p)

removeRL is like removeFL except with RL

removeCommon :: (MyEq p, Commute p) => (FL p :\/: FL p) -> FL p :\/: FL p

commuteWhatWeCanFL :: Commute p => (p :> FL p) -> FL p :> (p :> FL p)

commuteWhatWeCanRL :: Commute p => (RL p :> p) -> RL p :> (p :> RL p)

genCommuteWhatWeCanRL :: ((p :> p) -> Maybe (p :> p)) -> (RL p :> p) -> RL p :> (p :> RL p)

partitionFL

Arguments

:: Commute p

=> (p -> Bool)

predicate; if true we would like the patch in the left list

-> FL p

input FL

-> FL p :> (FL p :> FL p)

left, middle and right

split an FL into left and right lists according to a predicate, using commutation as necessary. If a patch does satisfy the predicate but cannot be commuted past one that does not satisfy the predicate, it goes in the right list.

partitionRL

Arguments

:: Commute p

=> (p -> Bool)

predicate; if true we would like the patch in the right list

-> RL p

input RL

-> RL p :> RL p

left and right results

split an RL into left and right lists according to a predicate, using commutation as necessary. If a patch does satisfy the predicate but cannot be commuted past one that does not satisfy the predicate, it goes in the left list.

simpleHeadPermutationsFL :: Commute p => FL p -> [FL p]

This is a minor variant of headPermutationsFL with each permutation is simply returned as a FL

headPermutationsRL :: Commute p => RL p -> [RL p]

headPermutationsRL is like headPermutationsFL, except that we operate on an RL (in other words, we are pushing things to the end of a patch sequence instead of to the beginning).

headPermutationsFL :: Commute p => FL p -> [p :> FL p]

headPermutationsFL p:>:ps returns all the permutations of the list in which one element of ps is commuted past p

Suppose we have a sequence of patches

  X h a y s-t-c k

Suppose furthermore that the patch c depends on t, which in turn depends on s. This function will return

 X :> h a y s t c k
 h :> X a y s t c k
 a :> X h y s t c k
 y :> X h a s t c k
 s :> X h a y t c k
 k :> X h a y s t c

removeSubsequenceFL :: (MyEq p, Commute p) => FL p -> FL p -> Maybe (FL p)

removeSubsequenceFL ab abc returns Just c' where all the patches in ab have been commuted out of it, if possible. If this is not possible for any reason (the set of patches ab is not actually a subset of abc, or they can't be commuted out) we return Nothing.

removeSubsequenceRL :: (MyEq p, Commute p) => RL p -> RL p -> Maybe (RL p)

removeSubsequenceRL is like removeSubsequenceFL except that it works on RL

partitionConflictingFL :: (Commute p1, Invert p1) => CommuteFn p1 p2 -> FL p1 -> p2 -> FL p1 :> FL p1

Partition a list into the patches that commute with the given patch and those that don't (including dependencies)

type CommuteFn p1 p2 = (p1 :> p2) -> Maybe (p2 :> p1)

CommuteFn is the basis of a general framework for building up commutation operations between different patch types in a generic manner. Unfortunately type classes are not well suited to the problem because of the multiple possible routes by which the commuter for (FL p1, FL p2) can be built out of the commuter for (p1, p2) - and more complicated problems when we start building multiple constructors on top of each other. The type class resolution machinery really can't cope with selecting some route, because it doesn't know that all possible routes should be equivalent.

selfCommuter :: Commute p => CommuteFn p p

Build a commuter between a patch and itself using the operation from the type class.

commuterIdRL :: CommuteFn p1 p2 -> CommuteFn p1 (RL p2)