File: IParen.lg

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{-

Demonstrates the use of `insert'.

	frown IParen.g

-}

> module IParen
> where
>
> newtype Tree                  =  Node [Tree]
>                                  deriving (Show)
>
> type Terminal                 =  Char
>
> type Result                   =  Maybe
>
> %{
>
> Terminal                      =  '(' | ')';
>
> Nonterminal                   =  pars {Tree};
>
> pars {Node []}                :  ;
>      {Node (x : xs)}          |  '(', pars {x}, ')', pars {Node xs};
>      {Node (x : xs)}          |  '(', pars {x}, insert ')', pars {Node xs};
>
> }%
>
> frown ts                      =  fail "syntax error"