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We also recommend that a + file or class name and description of purpose be included on the + same "printed page" as the copyright notice for easier + identification within third-party archives. + + Copyright 2018 Paul Young + + Licensed under the Apache License, Version 2.0 (the "License"); + you may not use this file except in compliance with the License. + You may obtain a copy of the License at + + http://www.apache.org/licenses/LICENSE-2.0 + + Unless required by applicable law or agreed to in writing, software + distributed under the License is distributed on an "AS IS" BASIS, + WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. + See the License for the specific language governing permissions and + limitations under the License. diff --git a/README.md b/README.md new file mode 100644 index 0000000..ec23eba --- /dev/null +++ b/README.md @@ -0,0 +1,15 @@ +# purescript-invertible-syntax + +A PureScript implementation of invertible syntax descriptions, from the paper [Invertible Syntax Descriptions: Unifying Parsing and Pretty Printing (Rendel and Ostermann 2010)](http://www.informatik.uni-marburg.de/~rendel/unparse/rendel10invertible.pdf). + +## Licensing + +This project is licensed under the terms of the Apache-2.0 license. + +However, some additional functionality not included in the paper has been included here, with inspiration taken from the Haskell package [`invertible-syntax`](http://hackage.haskell.org/package/invertible-syntax). The following copyright notice appears in conformance with its BSD-3-Clause license. + +``` +Copyright (c) 2010-11 University of Marburg + +All rights reserved. +``` diff --git a/bower.json b/bower.json new file mode 100644 index 0000000..2db8494 --- /dev/null +++ b/bower.json @@ -0,0 +1,26 @@ +{ + "name": "purescript-invertible-syntax", + "license": "Apache-2.0", + "repository": { + "type": "git", + "url": "git://github.com/paulyoung/purescript-invertible-syntax.git" + }, + "ignore": [ + "**/.*", + "node_modules", + "bower_components", + "output" + ], + "dependencies": { + "purescript-either": "^3.2.0", + "purescript-lists": "^4.12.0", + "purescript-maybe": "^3.1.0", + "purescript-partial-isomorphisms": "^1.0.0", + "purescript-prelude": "^3.3.0", + "purescript-strings": "^3.5.0", + "purescript-tuples": "^4.1.0" + }, + "devDependencies": { + "purescript-psci-support": "^3.0.0" + } +} diff --git a/src/Text/Syntax/Classes.purs b/src/Text/Syntax/Classes.purs new file mode 100644 index 0000000..f10ee27 --- /dev/null +++ b/src/Text/Syntax/Classes.purs @@ -0,0 +1,24 @@ +module Text.Syntax.Classes where + +import Prelude hiding (($), (<*>), apply, map) + +import Control.Isomorphism.Partial (class IsoFunctor) +import Data.Tuple (Tuple) + + +class ProductFunctor f where + apply :: forall a b. f a -> f b -> f (Tuple a b) + +infixr 6 apply as <*> + + +class Alternative f where + alt :: forall a. f a -> f a -> f a + empty :: forall a. f a + +infixl 3 alt as <|> + + +class (IsoFunctor d, ProductFunctor d, Alternative d) <= Syntax d where + pure :: forall a. Eq a => a -> d a + token :: d Char diff --git a/src/Text/Syntax/Combinators.purs b/src/Text/Syntax/Combinators.purs new file mode 100644 index 0000000..b499d2c --- /dev/null +++ b/src/Text/Syntax/Combinators.purs @@ -0,0 +1,118 @@ +-- | Derived combinators +module Text.Syntax.Combinators where + +import Prelude hiding ((<$>),(<*>),(<*),(*>),pure,unit) + +import Control.Isomorphism.Partial (Iso, inverse, (<$>)) +import Control.Isomorphism.Partial.Constructors (cons, left, nil, right) +import Control.Isomorphism.Partial.Derived (foldl) +import Control.Isomorphism.Partial.Prim (commute, element, ignore, unit) +import Data.Either (Either) +import Data.List (List(..), singleton) +import Data.Maybe (Maybe(..)) +import Data.String (uncons) +import Data.Tuple (Tuple(..)) +import Data.Unit as Unit +import Text.Syntax.Classes (class Syntax, pure, token, (<*>), (<|>)) + +-- Lexemes + +-- | `text` parses/prints a fixed text and consumes/produces a unit value. +text :: forall d. Syntax d => String -> d Unit +text s + | Just { head: c, tail: s' } <- uncons s = + inverse (element (Tuple Unit.unit Unit.unit)) + <$> (inverse (element c) <$> token) + <*> text s' + | otherwise = pure Unit.unit + +comma :: forall d. Syntax d => d Unit +comma = text "," + +dot :: forall d. Syntax d => d Unit +dot = text "." + +-- Repetition + +many :: forall d a. Syntax d => d a -> d (List a) +many p = nil <$> pure Unit.unit <|> cons <$> p <*> many p + +many1 :: forall d a. Syntax d => d a -> d (List a) +many1 p = cons <$> p <*> many p + +sepBy :: forall d a. Syntax d => d a -> d Unit -> d (List a) +sepBy x sep = nil <$> text "" <|> cons <$> x <*> many (sep *> x) + +-- | The `chainl1` combinator is used to parse a left-associative chain of +-- | infix operators. +chainl1 + :: forall d a b + . Syntax d + => d a + -> d b + -> Iso (Tuple a (Tuple b a)) a + -> d a +chainl1 arg op f = foldl f <$> arg <*> many (op <*> arg) + +-- Sequencing + +-- | This variant of `<*>` ignores its left result. In contrast to its +-- | counterpart derived from the `Apply` class, the ignored parts have type +-- | `d Unit` rather than `d b` because otherwise information relevant for +-- | pretty-printing would be lost. +applySecond :: forall d a. Syntax d => d Unit -> d a -> d a +applySecond p q = inverse unit <<< commute <$> p <*> q + +infixl 9 applySecond as *> + +-- | This variant of `<*>` ignores its right result. In contrast to its +-- | counterpart derived from the `Apply` class, the ignored parts have type +-- | `d Unit` rather than `d b` because otherwise information relevant for +-- | pretty-printing would be lost. +applyFirst :: forall d a. Syntax d => d a -> d Unit -> d a +applyFirst p q = inverse unit <$> p <*> q + +infixl 9 applyFirst as <* + +-- | The `between` function combines `*>` and `<*` in the obvious way. +between :: forall d a. Syntax d => d Unit -> d Unit -> d a -> d a +between p q r = p *> r <* q + +-- Alternation + +alt :: forall d a b. Syntax d => d a -> d b -> d (Either a b) +alt p q = (left <$> p) <|> (right <$> q) + +infixl 4 alt as <+> + +-- optional :: +-- optional + +-- Whitespace + +-- | Expressing whitespace +-- | +-- | Parsers and pretty printers treat whitespace differently. Parsers specify +-- | where whitespace is allowed or required to occur, while pretty printers +-- | specify how much whitespace is to be inserted at these locations. To +-- | account for these different roles of whitespace, the following three syntax +-- | descriptions provide fine-grained control over where whitespace is allowed, +-- | desired or required to occur. + +-- | `skipSpace` marks a position where whitespace is allowed to occur. It +-- | accepts arbitrary space while parsing, and produces no space while +-- | printing. +skipSpace :: forall d. Syntax d => d Unit +skipSpace = ignore Nil <$> many (text " ") + +-- | `optSpace` marks a position where whitespace is desired to occur. It +-- | accepts arbitrary space while parsing, and produces a single space +-- | character while printing. +optSpace :: forall d. Syntax d => d Unit +optSpace = ignore (singleton Unit.unit) <$> many (text " ") + +-- | `sepSpace` marks a position where whitespace is required to occur. It +-- | requires one or more space characters while parsing, and produces a single +-- | space character while printing. +sepSpace :: forall d. Syntax d => d Unit +sepSpace = text " " <* skipSpace diff --git a/src/Text/Syntax/Parser/Naive.purs b/src/Text/Syntax/Parser/Naive.purs new file mode 100644 index 0000000..79fd382 --- /dev/null +++ b/src/Text/Syntax/Parser/Naive.purs @@ -0,0 +1,37 @@ +module Text.Syntax.Parser.Naive where + +import Prelude hiding (apply) + +import Control.Isomorphism.Partial (class IsoFunctor, apply) +import Data.List (List(..)) +import Data.Maybe (Maybe(..)) +import Data.String (uncons) +import Data.Tuple (Tuple(..)) +import Text.Syntax.Classes (class Alternative, class ProductFunctor, class Syntax) + +newtype Parser a = Parser (String -> List (Tuple a String)) + +instance isoFunctorParser :: IsoFunctor Parser where + map iso (Parser p) = Parser f where + f s | Cons (Tuple x s') _ <- p s, Just y <- apply iso x = pure $ Tuple y s' + f _ = Nil + +instance productFunctorParser :: ProductFunctor Parser where + apply (Parser p) (Parser q) = Parser f where + f s | Cons (Tuple x s') _ <- p s, Cons (Tuple y s'') _ <- q s' = pure $ Tuple (Tuple x y) s'' + f _ = Nil + +instance alternativeParser :: Alternative Parser where + alt (Parser p) (Parser q) = Parser \s -> p s <> q s + empty = Parser \_ -> Nil + +instance syntaxParser :: Syntax Parser where + pure x = Parser \s -> pure $ Tuple x s + + token = Parser f where + f s | Just { head, tail } <- uncons s = pure $ Tuple head tail + f _ = Nil + +parse :: forall a. Parser a -> String -> List a +parse (Parser p) s | Cons (Tuple x "") _ <- p s = pure x +parse _ _ = Nil diff --git a/src/Text/Syntax/Printer/Naive.purs b/src/Text/Syntax/Printer/Naive.purs new file mode 100644 index 0000000..78774d1 --- /dev/null +++ b/src/Text/Syntax/Printer/Naive.purs @@ -0,0 +1,33 @@ +module Text.Syntax.Printer.Naive where + +import Prelude hiding (apply) + +import Control.Alt as Alt +import Control.Apply (lift2) +import Control.Isomorphism.Partial (class IsoFunctor, unapply) +import Data.Maybe (Maybe(..)) +import Data.String (singleton) +import Data.Tuple (Tuple(..)) +import Text.Syntax.Classes (class Alternative, class ProductFunctor, class Syntax) + +newtype Printer a = Printer (a -> Maybe String) + +instance isoFunctorPrinter :: IsoFunctor Printer where + map iso (Printer p) = Printer \b -> unapply iso b >>= p + +instance productFunctorPrinter :: ProductFunctor Printer where + apply (Printer p) (Printer q) = Printer \(Tuple x y) -> lift2 (<>) (p x) (q y) + +instance alternativePrinter :: Alternative Printer where + alt (Printer p) (Printer q) = Printer \s -> Alt.alt (p s) (q s) + empty = Printer \s -> Nothing + +instance syntaxPrinter :: Syntax Printer where + pure x = Printer f where + f y | x == y = Just "" + f _ = Nothing + + token = Printer \t -> Just $ singleton t + +print :: forall a. Printer a -> a -> Maybe String +print (Printer p) x = p x diff --git a/test/Main.purs b/test/Main.purs new file mode 100644 index 0000000..845d0f4 --- /dev/null +++ b/test/Main.purs @@ -0,0 +1,9 @@ +module Test.Main where + +import Prelude +import Control.Monad.Eff (Eff) +import Control.Monad.Eff.Console (CONSOLE, log) + +main :: forall e. Eff (console :: CONSOLE | e) Unit +main = do + log "You should add some tests."