implementation module SimpleParse

import StdList, StdTuple
from StdFunc import o

import Yard
import WhileCommon
import WhileLexer
import Simple

instance parse Stm
where
	parse cs = fst (runParser parser cs)
	where
		parser :: Parser Token Stm
		parser = liftM2 Compose parser` (item CompToken *> parser) <|> parser`

		parser` :: Parser Token Stm
		parser` = item ParenOpen *> parser <* item ParenClose
			<|> item SkipToken *> pure Skip
			<|> item IfToken *> liftM3 If
				pbexpr
				(item ThenToken *> parser)
				(item ElseToken *> parser`)
			<|> item WhileToken *> liftM2 While
				pbexpr
				(item DoToken *> parser`)
			<|> liftM2 Ass
				(toVar <$> satisfy isVarToken)
				(item AssToken *> paexpr)

		toVar (VarToken v) = v
		isVarToken (VarToken _) = True; isVarToken _ = False