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Add digits to Data.Syntax.Char.

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This commit is contained in:
Paweł Nowak 2014-11-29 16:57:23 +01:00
parent e5f2c1b682
commit c59546a612
1 changed files with 28 additions and 1 deletions
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29
Data/Syntax/Char.hs
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@ -20,7 +20,10 @@ module Data.Syntax.Char (
spaces,
spaces_,
spaces1,
endOfLine
endOfLine,
digitDec,
digitOct,
digitHex
) where
import Control.Lens.SemiIso
@ -68,3 +71,27 @@ spaces1 = constant (opoint ' ') /$/ takeWhile1 isSpace
-- | Accepts a single newline. Generates a newline.
endOfLine :: SyntaxChar syn seq => syn ()
endOfLine = char '\n'
-- | A decimal digit.
digitDec :: SyntaxChar syn seq => syn Int
digitDec = semiIso toChar toInt /$/ anyChar
where toInt c | isDigit c = Right (digitToInt c)
| otherwise = Left ("Expected a decimal digit, got " ++ [c])
toChar i | i >= 0 && i <= 9 = Right (intToDigit i)
| otherwise = Left ("Expected a decimal digit, got number " ++ show i)
-- | An octal digit.
digitOct :: SyntaxChar syn seq => syn Int
digitOct = semiIso toChar toInt /$/ anyChar
where toInt c | isOctDigit c = Right (digitToInt c)
| otherwise = Left ("Expected an octal digit, got " ++ [c])
toChar i | i >= 0 && i <= 7 = Right (intToDigit i)
| otherwise = Left ("Expected an octal digit, got number " ++ show i)
-- | A hex digit.
digitHex :: SyntaxChar syn seq => syn Int
digitHex = semiIso toChar toInt /$/ anyChar
where toInt c | isHexDigit c = Right (digitToInt c)
| otherwise = Left ("Expected a hex digit, got " ++ [c])
toChar i | i >= 0 && i <= 15 = Right (intToDigit i)
| otherwise = Left ("Expected a hex digit, got number " ++ show i)