darcs-2.5: src/Darcs/Patch/Permutations.hs
-- 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