-- Copyright (C) 2002-2003 David Roundy -- Copyright (C) 2009 Ganesh Sittampalam -- -- This program is free software; you can redistribute it and/or modify -- it under the terms of the GNU General Public License as published by -- the Free Software Foundation; either version 2, or (at your option) -- any later version. -- -- This program is distributed in the hope that it will be useful, -- but WITHOUT ANY WARRANTY; without even the implied warranty of -- MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the -- GNU General Public License for more details. -- -- You should have received a copy of the GNU General Public License -- along with this program; see the file COPYING. If not, write to -- the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, -- Boston, MA 02110-1301, USA. {-# OPTIONS_GHC -cpp -fglasgow-exts -fno-warn-orphans #-} {-# LANGUAGE CPP #-} -- , TypeOperators, PatternGuards #-} #include "gadts.h" module Darcs.Patch.Permutations ( removeFL, removeRL, removeCommon, commuteWhatWeCanFL, commuteWhatWeCanRL, genCommuteWhatWeCanRL, partitionFL, partitionRL, simpleHeadPermutationsFL, headPermutationsRL, headPermutationsFL, removeSubsequenceFL, removeSubsequenceRL, partitionConflictingFL, CommuteFn, selfCommuter, commuterIdRL, ) where import Data.Maybe ( catMaybes ) import Darcs.Patch.Patchy ( Commute, commute, commuteFLorComplain, commuteRL, Invert(..), invertFL, invertRL ) import Darcs.Witnesses.Ordered #include "impossible.h" -- |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. partitionFL :: Commute p => (FORALL(u v) p C(u v) -> Bool) -- ^predicate; if true we would like the patch in the "left" list -> FL p C(x y) -- ^input 'FL' -> ((FL p :> FL p :> FL p) C(x y)) -- ^"left", "middle" and "right" -- optimise by using an accumulating parameter to track all the "right" patches that we've found so far partitionFL' :: Commute p => (FORALL(u v) p C(u v) -> Bool) -> RL p C(a b) -- the "middle" patches found so far -> RL p C(b c) -- the "right" patches found so far -> FL p C(c d) -> ((FL p :> FL p :> FL p) C(a d)) partitionFL keepleft ps = partitionFL' keepleft NilRL NilRL ps partitionFL' _ middle right NilFL = (NilFL :> reverseRL middle :> reverseRL right) partitionFL' keepleft middle right (p :>: ps) | keepleft p = case commuteRL (right :> p) of Just (p' :> right') -> case commuteRL (middle :> p') of Just (p'' :> middle') -> case partitionFL' keepleft middle' right' ps of (a :> b :> c) -> (p'' :>: a :> b :> c) Nothing -> partitionFL' keepleft (p' :<: middle) right' ps Nothing -> case commuteWhatWeCanRL (right :> p) of (tomiddle :> p' :> right') -> partitionFL' keepleft (p' :<: tomiddle +<+ middle) right' ps | otherwise = partitionFL' keepleft middle (p :<: right) ps -- |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. partitionRL :: Commute p => (FORALL(u v) p C(u v) -> Bool) -- ^predicate; if true we would like the patch in the "right" list -> RL p C(x y) -- ^input 'RL' -> (RL p :> RL p) C(x y) -- ^"left" and "right" results -- optimise by using an accumulating parameter to track all the "left" patches that we've found so far partitionRL' :: Commute p => (FORALL(u v) p C(u v) -> Bool) -> RL p C(x z) -> FL p C(z y) -- the "left" patches found so far -> (RL p :> RL p) C(x y) partitionRL keepright ps = partitionRL' keepright ps NilFL partitionRL' _ NilRL qs = reverseFL qs :> NilRL partitionRL' keepright (p :<: ps) qs | keepright p, Right (qs' :> p') <- commuteFLorComplain (p :> qs) = case partitionRL' keepright ps qs' of a :> b -> a :> p' :<: b | otherwise = partitionRL' keepright ps (p :>: qs) commuteWhatWeCanFL :: Commute p => (p :> FL p) C(x y) -> (FL p :> p :> FL p) C(x y) commuteWhatWeCanFL (p :> x :>: xs) = case commute (p :> x) of Nothing -> case commuteWhatWeCanFL (x :> xs) of xs1 :> x' :> xs2 -> case commuteWhatWeCanFL (p :> xs1) of xs1' :> p' :> xs2' -> xs1' :> p' :> xs2' +>+ x' :>: xs2 Just (x' :> p') -> case commuteWhatWeCanFL (p' :> xs) of a :> p'' :> c -> x' :>: a :> p'' :> c commuteWhatWeCanFL (y :> NilFL) = NilFL :> y :> NilFL commuteWhatWeCanRL :: Commute p => (RL p :> p) C(x y) -> (RL p :> p :> RL p) C(x y) commuteWhatWeCanRL = genCommuteWhatWeCanRL commute genCommuteWhatWeCanRL :: (FORALL(a b) ((p :> p) C(a b) -> Maybe ((p :> p) C(a b)))) -> (RL p :> p) C(x y) -> (RL p :> p :> RL p) C(x y) genCommuteWhatWeCanRL com (x :<: xs :> p) = case com (x :> p) of Nothing -> case genCommuteWhatWeCanRL com (xs :> x) of xs1 :> x' :> xs2 -> case genCommuteWhatWeCanRL com (xs2 :> p) of xs1' :> p' :> xs2' -> xs1' +<+ x' :<: xs1 :> p' :> xs2' Just (p' :> x') -> case genCommuteWhatWeCanRL com (xs :> p') of a :> p'' :> c -> a :> p'' :> x' :<: c genCommuteWhatWeCanRL _ (NilRL :> y) = NilRL :> y :> NilRL removeCommon :: (MyEq p, Commute p) => (FL p :\/: FL p) C(x y) -> (FL p :\/: FL p) C(x y) removeCommon (xs :\/: NilFL) = xs :\/: NilFL removeCommon (NilFL :\/: xs) = NilFL :\/: xs removeCommon (xs :\/: ys) = rc xs (headPermutationsFL ys) where rc :: (MyEq p, Commute p) => FL p C(x y) -> [(p:>FL p) C(x z)] -> (FL p :\/: FL p) C(y z) rc nms ((n:>ns):_) | Just ms <- removeFL n nms = removeCommon (ms :\/: ns) rc ms [n:>ns] = ms :\/: n:>:ns rc ms (_:nss) = rc ms nss rc _ [] = impossible -- because we already checked for NilFL case -- | 'removeFL' @x xs@ removes @x@ from @xs@ if @x@ can be commuted to its head. -- Otherwise it returns 'Nothing' removeFL :: (MyEq p, Commute p) => p C(x y) -> FL p C(x z) -> Maybe (FL p C(y z)) removeFL x xs = r x $ headPermutationsFL xs where r :: (MyEq p, Commute p) => p C(x y) -> [(p:>FL p) C(x z)] -> Maybe (FL p C(y z)) r _ [] = Nothing r z ((z':>zs):zss) | IsEq <- z =\/= z' = Just zs | otherwise = r z zss -- | 'removeRL' is like 'removeFL' except with 'RL' removeRL :: (MyEq p, Commute p) => p C(y z) -> RL p C(x z) -> Maybe (RL p C(x y)) removeRL x xs = r x $ headPermutationsRL xs where r :: (MyEq p, Commute p) => p C(y z) -> [RL p C(x z)] -> Maybe (RL p C(x y)) r z ((z':<:zs):zss) | IsEq <- z =/\= z' = Just zs | otherwise = r z zss r _ _ = Nothing -- | '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'. removeSubsequenceFL :: (MyEq p, Commute p) => FL p C(a b) -> FL p C(a c) -> Maybe (FL p C(b c)) removeSubsequenceFL a b | lengthFL a > lengthFL b = Nothing | otherwise = rsFL a b where rsFL :: (MyEq p, Commute p) => FL p C(a b) -> FL p C(a c) -> Maybe (FL p C(b c)) rsFL NilFL ys = Just ys rsFL (x:>:xs) yys = removeFL x yys >>= removeSubsequenceFL xs -- | 'removeSubsequenceRL' is like @removeSubsequenceFL@ except that it works -- on 'RL' removeSubsequenceRL :: (MyEq p, Commute p) => RL p C(ab abc) -> RL p C(a abc) -> Maybe (RL p C(a ab)) removeSubsequenceRL a b | lengthRL a > lengthRL b = Nothing | otherwise = rsRL a b where rsRL :: (MyEq p, Commute p) => RL p C(ab abc) -> RL p C(a abc) -> Maybe (RL p C(a ab)) rsRL NilRL ys = Just ys rsRL (x:<:xs) yys = removeRL x yys >>= removeSubsequenceRL xs -- | This is a minor variant of 'headPermutationsFL' with each permutation -- is simply returned as a 'FL' simpleHeadPermutationsFL :: Commute p => FL p C(x y) -> [FL p C(x y)] simpleHeadPermutationsFL ps = map (\ (x:>xs) -> x:>:xs) $ headPermutationsFL ps -- | '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 headPermutationsFL :: Commute p => FL p C(x y) -> [(p :> FL p) C(x y)] headPermutationsFL NilFL = [] headPermutationsFL (p:>:ps) = (p:>ps) : catMaybes (map (swapfirstFL.(p:>)) $ headPermutationsFL ps) where swapfirstFL (p1:>p2:>xs) = do p2':>p1' <- commute (p1:>p2) Just $ p2':>p1':>:xs -- | '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). headPermutationsRL :: Commute p => RL p C(x y) -> [RL p C(x y)] headPermutationsRL NilRL = [] headPermutationsRL (p:<:ps) = (p:<:ps) : catMaybes (map (swapfirstRL.(p:<:)) $ headPermutationsRL ps) where swapfirstRL (p1:<:p2:<:xs) = do p1':>p2' <- commute (p2:>p1) Just $ p2':<:p1':<:xs swapfirstRL _ = Nothing instance (MyEq p, Commute p) => MyEq (FL p) where a =\/= b | lengthFL a /= lengthFL b = NotEq | otherwise = cmpSameLength a b where cmpSameLength :: FL p C(x y) -> FL p C(x z) -> EqCheck C(y z) cmpSameLength (x:>:xs) xys | Just ys <- removeFL x xys = cmpSameLength xs ys cmpSameLength NilFL NilFL = IsEq cmpSameLength _ _ = NotEq xs =/\= ys = reverseFL xs =/\= reverseFL ys instance (Invert p, Commute p) => Invert (FL p) where invert = reverseRL . invertFL identity = NilFL sloppyIdentity NilFL = IsEq sloppyIdentity (x:>:xs) | IsEq <- sloppyIdentity x = sloppyIdentity xs sloppyIdentity _ = NotEq instance (MyEq p, Commute p) => MyEq (RL p) where unsafeCompare = bug "Buggy use of unsafeCompare on RL" a =/\= b | lengthRL a /= lengthRL b = NotEq | otherwise = cmpSameLength a b where cmpSameLength :: RL p C(x y) -> RL p C(w y) -> EqCheck C(x w) cmpSameLength (x:<:xs) xys | Just ys <- removeRL x xys = cmpSameLength xs ys cmpSameLength NilRL NilRL = IsEq cmpSameLength _ _ = NotEq xs =\/= ys = reverseRL xs =\/= reverseRL ys instance (Commute p, Invert p) => Invert (RL p) where invert = reverseFL . invertRL identity = NilRL sloppyIdentity NilRL = IsEq sloppyIdentity (x:<:xs) | IsEq <- sloppyIdentity x = sloppyIdentity xs sloppyIdentity _ = NotEq -- |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. type CommuteFn p1 p2 = FORALL(x y) (p1 :> p2) C(x y) -> Maybe ((p2 :> p1) C(x y)) -- |Build a commuter between a patch and itself using the operation from the type class. selfCommuter :: Commute p => CommuteFn p p selfCommuter = commute commuterIdRL :: CommuteFn p1 p2 -> CommuteFn p1 (RL p2) commuterIdRL _ (x :> NilRL) = return (NilRL :> x) commuterIdRL commuter (x :> (y :<: ys)) = do ys' :> x' <- commuterIdRL commuter (x :> ys) y' :> x'' <- commuter (x' :> y) return ((y' :<: ys') :> x'') -- |Partition a list into the patches that commute with the given patch and those that don't (including dependencies) partitionConflictingFL :: (Commute p1, Invert p1) => CommuteFn p1 p2 -> FL p1 C(x y) -> p2 C(x z) -> (FL p1 :> FL p1) C(x y) partitionConflictingFL _ NilFL _ = (NilFL :> NilFL) partitionConflictingFL commuter (x :>: xs) y = case commuter (invert x :> y) of Nothing -> case commuteWhatWeCanFL (x :> xs) of xs_ok :> x' :> xs_deps -> case partitionConflictingFL commuter xs_ok y of xs_clean :> xs_conflicts -> xs_clean :> (xs_conflicts +>+ (x' :>: xs_deps)) Just (y' :> _) -> case partitionConflictingFL commuter xs y' of xs_clean :> xs_conflicts -> (x :>: xs_clean) :> xs_conflicts