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module Data.TeLML.Parser (Fragment(..), Document, parse) where
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import Data.Char (isAlpha, is |
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import Data.Char (isAlpha, isAlphaNum, isSpace)
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import Data.TeLML.Type
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type Result a = Either String (String, a)
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-- Parse a tag name of length >= 0.
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pTagName :: Parse String
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pTagName s = go s `bind` ensureLen
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pTagName s = go s `bind` ensureName
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where go i@(x:xs)
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| isAlpha x = (x:) `over` go xs
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| elem x "-_" = (x:) `over` go xs
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| otherwise = return (i, "")
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| isAlphaNum x = (x:) `over` go xs
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| elem x "-_" = (x:) `over` go xs
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| otherwise = return (i, "")
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go [] = throw "unexpected end-of-document while parsing tag"
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ensureLen (xs, name)
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| length name > 0 = return (xs, name)
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| otherwise = throw $ "expected tag name after `\\': " ++ show (name, xs)
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ensureName (xs, name)
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| length name == 0 =
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throw "expected tag name after `\\'"
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| not (isAlpha (head name)) =
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throw "tag names must begin with an alphabetic character"
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| otherwise = return (xs, name)
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-- Skip any space charaters, returning () for the first non-space
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-- character (including EOF).
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