61 lines
1.7 KiB
Haskell
61 lines
1.7 KiB
Haskell
{-# OPTIONS_GHC -W #-}
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module Parse.Pattern (term, expr) where
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import Control.Applicative ((<$>))
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import Data.Char (isUpper)
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import qualified Data.List as List
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import Text.Parsec hiding (newline,spaces,State)
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import Parse.Helpers
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import Parse.Literal
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import SourceSyntax.Literal
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import qualified SourceSyntax.Pattern as P
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basic :: IParser P.Pattern
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basic = choice
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[ char '_' >> return P.Anything
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, do v <- var
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return $ case v of
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"True" -> P.Literal (Boolean True)
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"False" -> P.Literal (Boolean False)
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c:_ | isUpper c -> P.Data v []
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_ -> P.Var v
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, P.Literal <$> literal
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]
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asPattern :: P.Pattern -> IParser P.Pattern
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asPattern pattern = do
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var <- optionMaybe (try (whitespace >> reserved "as" >> whitespace >> lowVar))
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return $ case var of
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Just v -> P.Alias v pattern
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Nothing -> pattern
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record :: IParser P.Pattern
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record = P.Record <$> brackets (commaSep1 lowVar)
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tuple :: IParser P.Pattern
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tuple = do
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ps <- parens (commaSep expr)
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return $ case ps of
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[p] -> p
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_ -> P.tuple ps
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list :: IParser P.Pattern
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list = P.list <$> braces (commaSep expr)
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term :: IParser P.Pattern
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term =
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(choice [ record, tuple, list, basic ]) <?> "pattern"
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patternConstructor :: IParser P.Pattern
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patternConstructor = do
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v <- List.intercalate "." <$> dotSep1 capVar
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case v of
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"True" -> return $ P.Literal (Boolean True)
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"False" -> return $ P.Literal (Boolean False)
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_ -> P.Data v <$> spacePrefix term
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expr :: IParser P.Pattern
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expr = do
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patterns <- consSep1 (patternConstructor <|> term)
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asPattern (foldr1 P.cons patterns) <?> "pattern"
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