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| author | MarLinn <MarLinn@users.noreply.github.com> | 2015-07-23 09:06:14 +0200 |
|---|---|---|
| committer | John MacFarlane <jgm@berkeley.edu> | 2015-07-23 15:37:01 -0700 |
| commit | f06809355527394f3c32c0e46e6f9cb48786b668 (patch) | |
| tree | 32b9489c146c003689cec8995ab8ac2d96a0d3c4 /src/Text/Pandoc/Readers/Odt/Arrows | |
| parent | 8390d935d8af944690736b7f2da5f2a58d97351b (diff) | |
| download | pandoc-f06809355527394f3c32c0e46e6f9cb48786b668.tar.gz | |
Added odt reader
Fully implemented features:
* Paragraphs
* Headers
* Basic styling
* Unordered lists
* Ordered lists
* External Links
* Internal Links
* Footnotes, Endnotes
* Blockquotes
Partly implemented features:
* Citations
Very basic, but pandoc can't do much more
* Tables
No headers, no sizing, limited styling
Diffstat (limited to 'src/Text/Pandoc/Readers/Odt/Arrows')
| -rw-r--r-- | src/Text/Pandoc/Readers/Odt/Arrows/State.hs | 253 | ||||
| -rw-r--r-- | src/Text/Pandoc/Readers/Odt/Arrows/Utils.hs | 497 |
2 files changed, 750 insertions, 0 deletions
diff --git a/src/Text/Pandoc/Readers/Odt/Arrows/State.hs b/src/Text/Pandoc/Readers/Odt/Arrows/State.hs new file mode 100644 index 000000000..310ca028e --- /dev/null +++ b/src/Text/Pandoc/Readers/Odt/Arrows/State.hs @@ -0,0 +1,253 @@ +{-# LANGUAGE Arrows #-} +{-# LANGUAGE TupleSections #-} +{-# LANGUAGE FlexibleInstances #-} +{- +Copyright (C) 2015 Martin Linnemann <theCodingMarlin@googlemail.com> + +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 of the License, 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; if not, write to the Free Software +Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA +-} + +{- | + Module : Text.Pandoc.Readers.Odt.Arrows.State + Copyright : Copyright (C) 2015 Martin Linnemann + License : GNU GPL, version 2 or above + + Maintainer : Martin Linnemann <theCodingMarlin@googlemail.com> + Stability : alpha + Portability : portable + +An arrow that transports a state. It is in essence a more powerful version of +the standard state monad. As it is such a simple extension, there are +other version out there that do exactly the same. +The implementation is duplicated, though, to add some useful features. +Most of these might be implemented without access to innards, but it's much +faster and easier to implement this way. +-} + +module Text.Pandoc.Readers.Odt.Arrows.State where + +import Prelude hiding ( foldr, foldl ) + +import qualified Control.Category as Cat +import Control.Arrow +import Control.Monad + +import Data.Monoid +import Data.Foldable + +import Text.Pandoc.Readers.Odt.Arrows.Utils +import Text.Pandoc.Readers.Odt.Generic.Fallible + + +newtype ArrowState state a b = ArrowState + { runArrowState :: (state, a) -> (state, b) } + +-- | Constructor +withState :: (state -> a -> (state, b)) -> ArrowState state a b +withState = ArrowState . uncurry + +-- | Constructor +withState' :: ((state, a) -> (state, b)) -> ArrowState state a b +withState' = ArrowState + +-- | Constructor +modifyState :: (state -> state ) -> ArrowState state a a +modifyState = ArrowState . first + +-- | Constructor +ignoringState :: ( a -> b ) -> ArrowState state a b +ignoringState = ArrowState . second + +-- | Constructor +fromState :: (state -> (state, b)) -> ArrowState state a b +fromState = ArrowState . (.fst) + +-- | Constructor +extractFromState :: (state -> b ) -> ArrowState state x b +extractFromState f = ArrowState $ \(state,_) -> (state, f state) + +-- | Constructor +withUnchangedState :: (state -> a -> b ) -> ArrowState state a b +withUnchangedState f = ArrowState $ \(state,a) -> (state, f state a) + +-- | Constructor +tryModifyState :: (state -> Either f state) + -> ArrowState state a (Either f a) +tryModifyState f = ArrowState $ \(state,a) + -> (state,).Left ||| (,Right a) $ f state + +instance Cat.Category (ArrowState s) where + id = ArrowState id + arrow2 . arrow1 = ArrowState $ (runArrowState arrow2).(runArrowState arrow1) + +instance Arrow (ArrowState state) where + arr = ignoringState + first a = ArrowState $ \(s,(aF,aS)) + -> second (,aS) $ runArrowState a (s,aF) + second a = ArrowState $ \(s,(aF,aS)) + -> second (aF,) $ runArrowState a (s,aS) + +instance ArrowChoice (ArrowState state) where + left a = ArrowState $ \(s,e) -> case e of + Left l -> second Left $ runArrowState a (s,l) + Right r -> (s, Right r) + right a = ArrowState $ \(s,e) -> case e of + Left l -> (s, Left l) + Right r -> second Right $ runArrowState a (s,r) + +instance ArrowLoop (ArrowState state) where + loop a = ArrowState $ \(s, x) + -> let (s', (x', _d)) = runArrowState a (s, (x, _d)) + in (s', x') + +instance ArrowApply (ArrowState state) where + app = ArrowState $ \(s, (f,b)) -> runArrowState f (s,b) + + +-- | Embedding of a state arrow in a state arrow with a different state type. +switchState :: (s -> s') -> (s' -> s) -> ArrowState s' x y -> ArrowState s x y +switchState there back a = ArrowState $ first there + >>> runArrowState a + >>> first back + +-- | Lift a state arrow to modify the state of an arrow +-- with a different state type. +liftToState :: (s -> s') -> ArrowState s' s s -> ArrowState s x x +liftToState unlift a = modifyState $ unlift &&& id + >>> runArrowState a + >>> snd + +-- | Switches the type of the state temporarily. +-- Drops the intermediate result state, behaving like the identity arrow, +-- save for side effects in the state. +withSubState :: ArrowState s x s2 -> ArrowState s2 s s -> ArrowState s x x +withSubState unlift a = keepingTheValue (withSubState unlift a) >>^ fst + +-- | Switches the type of the state temporarily. +-- Returns the resulting sub-state. +withSubState' :: ArrowState s x s' -> ArrowState s' s s -> ArrowState s x s' +withSubState' unlift a = ArrowState $ runArrowState unlift + >>> switch + >>> runArrowState a + >>> switch + where switch (x,y) = (y,x) + +-- | Switches the type of the state temporarily. +-- Drops the intermediate result state, behaving like a fallible +-- identity arrow, save for side effects in the state. +withSubStateF :: ArrowState s x (Either f s') + -> ArrowState s' s (Either f s ) + -> ArrowState s x (Either f x ) +withSubStateF unlift a = keepingTheValue (withSubStateF' unlift a) + >>^ spreadChoice + >>^ fmap fst + +-- | Switches the type of the state temporarily. +-- Returns the resulting sub-state. +withSubStateF' :: ArrowState s x (Either f s') + -> ArrowState s' s (Either f s ) + -> ArrowState s x (Either f s') +withSubStateF' unlift a = ArrowState go + where go p@(s,_) = tryRunning unlift + ( tryRunning a (second Right) ) + p + where tryRunning a' b v = case runArrowState a' v of + (_ , Left f) -> (s, Left f) + (x , Right y) -> b (y,x) + +-- | Fold a state arrow through something 'Foldable'. Collect the results +-- in a 'Monoid'. +-- Intermediate form of a fold between one with "only" a 'Monoid' +-- and one with any function. +foldS :: (Foldable f, Monoid m) => ArrowState s x m -> ArrowState s (f x) m +foldS a = ArrowState $ \(s,f) -> foldr a' (s,mempty) f + where a' x (s',m) = second (m <>) $ runArrowState a (s',x) + +-- | Fold a state arrow through something 'Foldable'. Collect the results +-- in a 'Monoid'. +-- Intermediate form of a fold between one with "only" a 'Monoid' +-- and one with any function. +foldSL :: (Foldable f, Monoid m) => ArrowState s x m -> ArrowState s (f x) m +foldSL a = ArrowState $ \(s,f) -> foldl a' (s,mempty) f + where a' (s',m) x = second (m <>) $ runArrowState a (s',x) + +-- | Fold a fallible state arrow through something 'Foldable'. Collect the +-- results in a 'Monoid'. +-- Intermediate form of a fold between one with "only" a 'Monoid' +-- and one with any function. +-- If the iteration fails, the state will be reset to the initial one. +foldS' :: (Foldable f, Monoid m) + => ArrowState s x (Either e m) + -> ArrowState s (f x) (Either e m) +foldS' a = ArrowState $ \(s,f) -> foldr (a' s) (s,Right mempty) f + where a' s x (s',Right m) = case runArrowState a (s',x) of + (s'',Right m') -> (s'', Right (m <> m')) + (_ ,Left e ) -> (s , Left e) + a' _ _ e = e + +-- | Fold a fallible state arrow through something 'Foldable'. Collect the +-- results in a 'Monoid'. +-- Intermediate form of a fold between one with "only" a 'Monoid' +-- and one with any function. +-- If the iteration fails, the state will be reset to the initial one. +foldSL' :: (Foldable f, Monoid m) + => ArrowState s x (Either e m) + -> ArrowState s (f x) (Either e m) +foldSL' a = ArrowState $ \(s,f) -> foldl (a' s) (s,Right mempty) f + where a' s (s',Right m) x = case runArrowState a (s',x) of + (s'',Right m') -> (s'', Right (m <> m')) + (_ ,Left e ) -> (s , Left e) + a' _ e _ = e + +-- | Fold a state arrow through something 'Foldable'. Collect the results in a +-- 'MonadPlus'. +iterateS :: (Foldable f, MonadPlus m) + => ArrowState s x y + -> ArrowState s (f x) (m y) +iterateS a = ArrowState $ \(s,f) -> foldr a' (s,mzero) f + where a' x (s',m) = second ((mplus m).return) $ runArrowState a (s',x) + +-- | Fold a state arrow through something 'Foldable'. Collect the results in a +-- 'MonadPlus'. +iterateSL :: (Foldable f, MonadPlus m) + => ArrowState s x y + -> ArrowState s (f x) (m y) +iterateSL a = ArrowState $ \(s,f) -> foldl a' (s,mzero) f + where a' (s',m) x = second ((mplus m).return) $ runArrowState a (s',x) + + +-- | Fold a fallible state arrow through something 'Foldable'. +-- Collect the results in a 'MonadPlus'. +-- If the iteration fails, the state will be reset to the initial one. +iterateS' :: (Foldable f, MonadPlus m) + => ArrowState s x (Either e y ) + -> ArrowState s (f x) (Either e (m y)) +iterateS' a = ArrowState $ \(s,f) -> foldr (a' s) (s,Right mzero) f + where a' s x (s',Right m) = case runArrowState a (s',x) of + (s'',Right m') -> (s'',Right $ mplus m $ return m') + (_ ,Left e ) -> (s ,Left e ) + a' _ _ e = e + +-- | Fold a fallible state arrow through something 'Foldable'. +-- Collect the results in a 'MonadPlus'. +-- If the iteration fails, the state will be reset to the initial one. +iterateSL' :: (Foldable f, MonadPlus m) + => ArrowState s x (Either e y ) + -> ArrowState s (f x) (Either e (m y)) +iterateSL' a = ArrowState $ \(s,f) -> foldl (a' s) (s,Right mzero) f + where a' s (s',Right m) x = case runArrowState a (s',x) of + (s'',Right m') -> (s'',Right $ mplus m $ return m') + (_ ,Left e ) -> (s ,Left e ) + a' _ e _ = e diff --git a/src/Text/Pandoc/Readers/Odt/Arrows/Utils.hs b/src/Text/Pandoc/Readers/Odt/Arrows/Utils.hs new file mode 100644 index 000000000..9710973b3 --- /dev/null +++ b/src/Text/Pandoc/Readers/Odt/Arrows/Utils.hs @@ -0,0 +1,497 @@ +{- +Copyright (C) 2015 Martin Linnemann <theCodingMarlin@googlemail.com> + +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 of the License, 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; if not, write to the Free Software +Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA +-} + +{- | + Module : Text.Pandoc.Readers.Odt.Arrows.Utils + Copyright : Copyright (C) 2015 Martin Linnemann + License : GNU GPL, version 2 or above + + Maintainer : Martin Linnemann <theCodingMarlin@googlemail.com> + Stability : alpha + Portability : portable + +Utility functions for Arrows (Kleisli monads). + +Some general notes on notation: + +* "^" is meant to stand for a pure function that is lifted into an arrow +based on its usage for that purpose in "Control.Arrow". +* "?" is meant to stand for the usage of a 'FallibleArrow' or a pure function +with an equivalent return value. +* "_" stands for the dropping of a value. +-} + +-- We export everything +module Text.Pandoc.Readers.Odt.Arrows.Utils where + +import Control.Arrow +import Control.Monad ( join, MonadPlus(..) ) + +import Data.Monoid +import qualified Data.Foldable as F + +import Text.Pandoc.Readers.Odt.Generic.Fallible +import Text.Pandoc.Readers.Odt.Generic.Utils + + +and2 :: (Arrow a) => a b c -> a b c' -> a b (c,c') +and2 = (&&&) + +and3 :: (Arrow a) + => a b c0->a b c1->a b c2 + -> a b (c0,c1,c2 ) +and4 :: (Arrow a) + => a b c0->a b c1->a b c2->a b c3 + -> a b (c0,c1,c2,c3 ) +and5 :: (Arrow a) + => a b c0->a b c1->a b c2->a b c3->a b c4 + -> a b (c0,c1,c2,c3,c4 ) +and6 :: (Arrow a) + => a b c0->a b c1->a b c2->a b c3->a b c4->a b c5 + -> a b (c0,c1,c2,c3,c4,c5 ) +and7 :: (Arrow a) + => a b c0->a b c1->a b c2->a b c3->a b c4->a b c5->a b c6 + -> a b (c0,c1,c2,c3,c4,c5,c6 ) +and8 :: (Arrow a) + => a b c0->a b c1->a b c2->a b c3->a b c4->a b c5->a b c6->a b c7 + -> a b (c0,c1,c2,c3,c4,c5,c6,c7) + +and3 a b c = (and2 a b ) &&& c + >>^ \((z,y ) , x) -> (z,y,x ) +and4 a b c d = (and3 a b c ) &&& d + >>^ \((z,y,x ) , w) -> (z,y,x,w ) +and5 a b c d e = (and4 a b c d ) &&& e + >>^ \((z,y,x,w ) , v) -> (z,y,x,w,v ) +and6 a b c d e f = (and5 a b c d e ) &&& f + >>^ \((z,y,x,w,v ) , u) -> (z,y,x,w,v,u ) +and7 a b c d e f g = (and6 a b c d e f ) &&& g + >>^ \((z,y,x,w,v,u ) , t) -> (z,y,x,w,v,u,t ) +and8 a b c d e f g h = (and7 a b c d e f g) &&& h + >>^ \((z,y,x,w,v,u,t) , s) -> (z,y,x,w,v,u,t,s) + +liftA2 :: (Arrow a) => (x -> y -> z) -> a b x -> a b y -> a b z +liftA2 f a b = a &&& b >>^ uncurry f + +liftA3 :: (Arrow a) => (z->y->x -> r) + -> a b z->a b y->a b x + -> a b r +liftA4 :: (Arrow a) => (z->y->x->w -> r) + -> a b z->a b y->a b x->a b w + -> a b r +liftA5 :: (Arrow a) => (z->y->x->w->v -> r) + -> a b z->a b y->a b x->a b w->a b v + -> a b r +liftA6 :: (Arrow a) => (z->y->x->w->v->u -> r) + -> a b z->a b y->a b x->a b w->a b v->a b u + -> a b r +liftA7 :: (Arrow a) => (z->y->x->w->v->u->t -> r) + -> a b z->a b y->a b x->a b w->a b v->a b u->a b t + -> a b r +liftA8 :: (Arrow a) => (z->y->x->w->v->u->t->s -> r) + -> a b z->a b y->a b x->a b w->a b v->a b u->a b t->a b s + -> a b r + +liftA3 fun a b c = and3 a b c >>^ uncurry3 fun +liftA4 fun a b c d = and4 a b c d >>^ uncurry4 fun +liftA5 fun a b c d e = and5 a b c d e >>^ uncurry5 fun +liftA6 fun a b c d e f = and6 a b c d e f >>^ uncurry6 fun +liftA7 fun a b c d e f g = and7 a b c d e f g >>^ uncurry7 fun +liftA8 fun a b c d e f g h = and8 a b c d e f g h >>^ uncurry8 fun + +liftA :: (Arrow a) => (y -> z) -> a b y -> a b z +liftA fun a = a >>^ fun + + +-- | Duplicate a value to subsequently feed it into different arrows. +-- Can almost always be replaced with '(&&&)', 'keepingTheValue', +-- or even '(|||)'. +-- Aequivalent to +-- > returnA &&& returnA +duplicate :: (Arrow a) => a b (b,b) +duplicate = arr $ join (,) + +-- | Lifts the combination of two values into an arrow. +joinOn :: (Arrow a) => (x -> y -> z) -> a (x,y) z +joinOn = arr.uncurry + +-- | Applies a function to the uncurried result-pair of an arrow-application. +-- (The §-symbol was chosen to evoke an association with pairs through the +-- shared first character) +(>>§) :: (Arrow a) => a x (b,c) -> (b -> c -> d) -> a x d +a >>§ f = a >>^ uncurry f + +-- | '(>>§)' with its arguments flipped +(§<<) :: (Arrow a) => (b -> c -> d) -> a x (b,c) -> a x d +(§<<) = flip (>>§) + +-- | Precomposition with an uncurried function +(§>>) :: (Arrow a) => (b -> c -> d) -> a d r -> a (b,c) r +f §>> a = uncurry f ^>> a + +-- | Precomposition with an uncurried function (right to left variant) +(<<§) :: (Arrow a) => a d r -> (b -> c -> d) -> a (b,c) r +(<<§) = flip (§>>) + +infixr 2 >>§, §<<, §>>, <<§ + + +-- | Duplicate a value and apply an arrow to the second instance. +-- Aequivalent to +-- > \a -> duplicate >>> second a +-- or +-- > \a -> returnA &&& a +keepingTheValue :: (Arrow a) => a b c -> a b (b,c) +keepingTheValue a = returnA &&& a + +-- | Duplicate a value and apply an arrow to the first instance. +-- Aequivalent to +-- > \a -> duplicate >>> first a +-- or +-- > \a -> a &&& returnA +keepingTheValue' :: (Arrow a) => a b c -> a b (c,b) +keepingTheValue' a = a &&& returnA + +-- | 'bind' from the "Maybe"-Monad lifted into an 'ArrowChoice'. +-- Actually, it's the more complex '(>=>)', because 'bind' alone does not +-- combine as nicely in arrow form. +-- The current implementation is not the most efficient one, because it can +-- not return directly if a 'Nothing' is encountered. That in turn follows +-- from the type system, as 'Nothing' has an "invisible" type parameter that +-- can not be dropped early. +-- +-- Also, there probably is a way to generalize this to other monads +-- or applicatives, but I'm leaving that as an exercise to the reader. +-- I have a feeling there is a new Arrow-typeclass to be found that is less +-- restrictive than 'ArrowApply'. If it is already out there, +-- I have not seen it yet. ('ArrowPlus' for example is not general enough.) +(>>>=) :: (ArrowChoice a) => a x (Maybe b) -> a b (Maybe c) -> a x (Maybe c) +a1 >>>= a2 = a1 >>> maybeToChoice >>> right a2 >>> choiceToMaybe >>^ join + +infixr 2 >>>= + +-- | 'mplus' Lifted into an arrow. No 'ArrowPlus' required. +-- (But still different from a true bind) +(>++<) :: (Arrow a, MonadPlus m) => a x (m b) -> a x (m b) -> a x (m b) +(>++<) = liftA2 mplus + +-- | Left-compose with a pure function +leftLift :: (ArrowChoice a) => (l -> l') -> a (Either l r) (Either l' r) +leftLift = left.arr + +-- | Right-compose with a pure function +rightLift :: (ArrowChoice a) => (r -> r') -> a (Either l r) (Either l r') +rightLift = right.arr + + +( ^+++ ) :: (ArrowChoice a) => (b -> c) -> a b' c' -> a (Either b b') (Either c c') +( +++^ ) :: (ArrowChoice a) => a b c -> (b' -> c') -> a (Either b b') (Either c c') +( ^+++^ ) :: (ArrowChoice a) => (b -> c) -> (b' -> c') -> a (Either b b') (Either c c') + +l ^+++ r = leftLift l >>> right r +l +++^ r = left l >>> rightLift r +l ^+++^ r = leftLift l >>> rightLift r + +infixr 2 ^+++, +++^, ^+++^ + +( ^||| ) :: (ArrowChoice a) => (b -> d) -> a c d -> a (Either b c) d +( |||^ ) :: (ArrowChoice a) => a b d -> (c -> d) -> a (Either b c) d +( ^|||^ ) :: (ArrowChoice a) => (b -> d) -> (c -> d) -> a (Either b c) d + +l ^||| r = arr l ||| r +l |||^ r = l ||| arr r +l ^|||^ r = arr l ||| arr r + +infixr 2 ^||| , |||^, ^|||^ + +( ^&&& ) :: (Arrow a) => (b -> c) -> a b c' -> a b (c,c') +( &&&^ ) :: (Arrow a) => a b c -> (b -> c') -> a b (c,c') +( ^&&&^ ) :: (Arrow a) => (b -> c) -> (b -> c') -> a b (c,c') + +l ^&&& r = arr l &&& r +l &&&^ r = l &&& arr r +l ^&&&^ r = arr l &&& arr r + +infixr 3 ^&&&, &&&^, ^&&&^ + +( ^*** ) :: (Arrow a) => (b -> c) -> a b' c' -> a (b,b') (c,c') +( ***^ ) :: (Arrow a) => a b c -> (b' -> c') -> a (b,b') (c,c') +( ^***^ ) :: (Arrow a) => (b -> c) -> (b' -> c') -> a (b,b') (c,c') + +l ^*** r = arr l *** r +l ***^ r = l *** arr r +l ^***^ r = arr l *** arr r + +infixr 3 ^***, ***^, ^***^ + +-- | A version of +-- +-- >>> \p -> arr (\x -> if p x the Right x else Left x) +-- +-- but with p being an arrow +choose :: (ArrowChoice a) => a b Bool -> a b (Either b b) +choose checkValue = keepingTheValue checkValue >>^ select + where select (x,True ) = Right x + select (x,False ) = Left x + +-- | Converts @Right a@ into @Just a@ and @Left _@ into @Nothing@. +choiceToMaybe :: (ArrowChoice a) => a (Either l r) (Maybe r) +choiceToMaybe = arr eitherToMaybe + +-- | Converts @Nothing@ into @Left ()@ and @Just a@ into @Right a@. +maybeToChoice :: (ArrowChoice a) => a (Maybe b) (Fallible b) +maybeToChoice = arr maybeToEither + +-- | Lifts a constant value into an arrow +returnV :: (Arrow a) => c -> a x c +returnV = arr.const + +-- | 'returnA' dropping everything +returnA_ :: (Arrow a) => a _b () +returnA_ = returnV () + +-- | Wrapper for an arrow that can be evaluated im parallel. All +-- Arrows can be evaluated in parallel, as long as they return a +-- monoid. +newtype ParallelArrow a b c = CoEval { evalParallelArrow :: a b c } + deriving (Eq, Ord, Show) + +instance (Arrow a, Monoid m) => Monoid (ParallelArrow a b m) where + mempty = CoEval $ returnV mempty + (CoEval a) `mappend` (CoEval ~b) = CoEval $ a &&& b >>§ mappend + +-- | Evaluates a collection of arrows in a parallel fashion. +-- +-- This is in essence a fold of '(&&&)' over the collection, +-- so the actual execution order and parallelity depends on the +-- implementation of '(&&&)' in the arrow in question. +-- The default implementation of '(&&&)' for example keeps the +-- order as given in the collection. +-- +-- This function can be seen as a generalization of +-- 'Control.Applicative.sequenceA' to arrows or as an alternative to +-- a fold with 'Control.Applicative.WrappedArrow', which +-- substitutes the monoid with function application. +-- +coEval :: (Arrow a, F.Foldable f, Monoid m) => f (a b m) -> a b m +coEval = evalParallelArrow . (F.foldMap CoEval) + +-- | Defines Left as failure, Right as success +type FallibleArrow a input failure success = a input (Either failure success) + +type ReFallibleArrow a failure success success' + = FallibleArrow a (Either failure success) failure success' + +-- | Wrapper for fallible arrows. Fallible arrows are all arrows that return +-- an Either value where left is a faliure and right is a success value. +newtype AlternativeArrow a input failure success + = TryArrow { evalAlternativeArrow :: FallibleArrow a input failure success } + + +instance (ArrowChoice a, Monoid failure) + => Monoid (AlternativeArrow a input failure success) where + mempty = TryArrow $ returnV $ Left mempty + (TryArrow a) `mappend` (TryArrow b) + = TryArrow $ a &&& b + >>^ \(a',~b') + -> ( (\a'' -> left (mappend a'') b') ||| Right ) + a' + +-- | Evaluates a collection of fallible arrows, trying each one in succession. +-- Left values are interpreted as failures, right values as successes. +-- +-- The evaluation is stopped once an arrow succeeds. +-- Up to that point, all failures are collected in the failure-monoid. +-- Note that '()' is a monoid, and thus can serve as a failure-collector if +-- you are uninterested in the exact failures. +-- +-- This is in essence a fold of '(&&&)' over the collection, enhanced with a +-- little bit of repackaging, so the actual execution order depends on the +-- implementation of '(&&&)' in the arrow in question. +-- The default implementation of '(&&&)' for example keeps the +-- order as given in the collection. +-- +tryArrows :: (ArrowChoice a, F.Foldable f, Monoid failure) + => f (FallibleArrow a b failure success) + -> FallibleArrow a b failure success +tryArrows = evalAlternativeArrow . (F.foldMap TryArrow) + +-- +liftSuccess :: (ArrowChoice a) + => (success -> success') + -> ReFallibleArrow a failure success success' +liftSuccess = rightLift + +-- +liftAsSuccess :: (ArrowChoice a) + => a x success + -> FallibleArrow a x failure success +liftAsSuccess a = a >>^ Right + +-- +asFallibleArrow :: (ArrowChoice a) + => a x success + -> FallibleArrow a x failure success +asFallibleArrow a = a >>^ Right + +-- | Raises an error into a 'ReFallibleArrow' if the arrow is already in +-- "error mode" +liftError :: (ArrowChoice a, Monoid failure) + => failure + -> ReFallibleArrow a failure success success +liftError e = leftLift (e <>) + +-- | Raises an error into a 'FallibleArrow', droping both the arrow input +-- and any previously stored error value. +_raiseA :: (ArrowChoice a) + => failure + -> FallibleArrow a x failure success +_raiseA e = returnV (Left e) + +-- | Raises an empty error into a 'FallibleArrow', droping both the arrow input +-- and any previously stored error value. +_raiseAEmpty :: (ArrowChoice a, Monoid failure) + => FallibleArrow a x failure success +_raiseAEmpty = _raiseA mempty + +-- | Raises an error into a 'ReFallibleArrow', possibly appending the new error +-- to an existing one +raiseA :: (ArrowChoice a, Monoid failure) + => failure + -> ReFallibleArrow a failure success success +raiseA e = arr $ Left.(either (<> e) (const e)) + +-- | Raises an empty error into a 'ReFallibleArrow'. If there already is an +-- error, nothing changes. +-- (Note that this function is only aequivalent to @raiseA mempty@ iff the +-- failure monoid follows the monoid laws.) +raiseAEmpty :: (ArrowChoice a, Monoid failure) + => ReFallibleArrow a failure success success +raiseAEmpty = arr (fromRight (const mempty) >>> Left) + + +-- | Execute the second arrow if the first succeeds +(>>?) :: (ArrowChoice a, Monoid failure) + => FallibleArrow a x failure success + -> FallibleArrow a success failure success' + -> FallibleArrow a x failure success' +a >>? b = a >>> Left ^||| b + +-- | Execute the lifted second arrow if the first succeeds +(>>?^) :: (ArrowChoice a, Monoid failure) + => FallibleArrow a x failure success + -> (success -> success') + -> FallibleArrow a x failure success' +a >>?^ f = a >>^ Left ^|||^ Right . f + +-- | Execute the lifted second arrow if the first succeeds +(>>?^?) :: (ArrowChoice a, Monoid failure) + => FallibleArrow a x failure success + -> (success -> Either failure success') + -> FallibleArrow a x failure success' +a >>?^? b = a >>> Left ^|||^ b + +-- | Execute the second arrow if the lifted first arrow succeeds +(^>>?) :: (ArrowChoice a, Monoid failure) + => (x -> Either failure success) + -> FallibleArrow a success failure success' + -> FallibleArrow a x failure success' +a ^>>? b = a ^>> Left ^||| b + +-- | Execute the lifted second arrow if the lifted first arrow succeeds +(^>>?^) :: (ArrowChoice a, Monoid failure) + => (x -> Either failure success) + -> (success -> success') + -> FallibleArrow a x failure success' +a ^>>?^ f = arr $ a >>> right f + +-- | Execute the lifted second arrow if the lifted first arrow succeeds +(^>>?^?) :: (ArrowChoice a, Monoid failure) + => (x -> Either failure success) + -> (success -> Either failure success') + -> FallibleArrow a x failure success' +a ^>>?^? f = a ^>> Left ^|||^ f + +-- | Execute the second, non-fallible arrow if the first arrow succeeds +(>>?!) :: (ArrowChoice a, Monoid failure) + => FallibleArrow a x failure success + -> a success success' + -> FallibleArrow a x failure success' +a >>?! f = a >>> right f + +--- +(>>?§) :: (ArrowChoice a, Monoid f) + => FallibleArrow a x f (b,b') + -> (b -> b' -> c) + -> FallibleArrow a x f c +a >>?§ f = a >>?^ (uncurry f) + +--- +(^>>?§) :: (ArrowChoice a, Monoid f) + => (x -> Either f (b,b')) + -> (b -> b' -> c) + -> FallibleArrow a x f c +a ^>>?§ f = arr a >>?^ (uncurry f) + +--- +(>>?§?) :: (ArrowChoice a, Monoid f) + => FallibleArrow a x f (b,b') + -> (b -> b' -> (Either f c)) + -> FallibleArrow a x f c +a >>?§? f = a >>?^? (uncurry f) + +infixr 1 >>?, >>?^, >>?^? +infixr 1 ^>>?, ^>>?^, ^>>?^?, >>?! +infixr 1 >>?§, ^>>?§, >>?§? + +-- | Keep values that are Right, replace Left values by a constant. +ifFailedUse :: (ArrowChoice a) => v -> a (Either f v) v +ifFailedUse v = arr $ either (const v) id + +-- | '(&&)' lifted into an arrow +(<&&>) :: (Arrow a) => a x Bool -> a x Bool -> a x Bool +(<&&>) = liftA2 (&&) + +-- | '(||)' lifted into an arrow +(<||>) :: (Arrow a) => a x Bool -> a x Bool -> a x Bool +(<||>) = liftA2 (||) + +-- | An equivalent of '(&&)' in a fallible arrow +(>&&<) :: (ArrowChoice a, Monoid f) => FallibleArrow a x f s + -> FallibleArrow a x f s' + -> FallibleArrow a x f (s,s') +(>&&<) = liftA2 chooseMin + +-- | An equivalent of '(||)' in some forms of fallible arrows +(>||<) :: (ArrowChoice a, Monoid f, Monoid s) => FallibleArrow a x f s + -> FallibleArrow a x f s + -> FallibleArrow a x f s +(>||<) = liftA2 chooseMax + +-- | An arrow version of a short-circuit (<|>) +ifFailedDo :: (ArrowChoice a) + => FallibleArrow a x f y + -> FallibleArrow a x f y + -> FallibleArrow a x f y +ifFailedDo a b = keepingTheValue a >>> repackage ^>> (b |||^ Right) + where repackage (x , Left _) = Left x + repackage (_ , Right y) = Right y + +infixr 4 <&&>, <||>, >&&<, >||< +infixr 1 `ifFailedDo` + + |