45 lines
1.2 KiB
Haskell
45 lines
1.2 KiB
Haskell
module Parser where
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import Text.ParserCombinators.Parsec
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import Expression
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-- Receives a string, parses it, and returns an expression
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parseExpression :: String -> Either ParseError Expression
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parseExpression s = do
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e <- parse anyExpressionParser "" s
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return e
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-- Parser for any possible expression
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anyExpressionParser :: GenParser Char st Expression
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anyExpressionParser = numberParser <|> symbolParser <|> sexprParser
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-- Parser for an S-expr
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sexprParser :: GenParser Char st Expression
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sexprParser = do
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_ <- spaces
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_ <- char '('
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es <- many1 (try $ spaces >> anyExpressionParser)
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_ <- spaces
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_ <- char ')' >> spaces
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return $ SExpr es
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-- Parser for a symbol
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symbolParser :: GenParser Char st Expression
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symbolParser = Symbol <$> do
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c <- symbolChar
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cs <- many (symbolChar <|> digit)
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return $ c:cs
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where symbolChar = letter <|> oneOf "!#$%&*+-/:<=>?@\\^_`~"
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-- Parser for a number
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numberParser :: GenParser Char st Expression
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numberParser = do
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intPart <- many1 digit
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decPart <- option "" parseDecPart
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return $ Number $ read (intPart ++ decPart)
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where parseDecPart = do
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p <- char '.'
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dec <- many digit
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return $ p:dec
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