Re: Need help specifying a grammar rule

> [ how do you say this in yacc? ]
> expression ::=
> relation { AND relation }
> | relation { AND THEN relation }
> | relation { OR relation }
> | relation { OR ELSE relation }
> | relation { XOR relation }


> [Unless I'm missing something, you should be able to write this pretty
> much as is with some precedence rules. -John]


With the curly brace metasyntax removed, these are essentially the
classic:


expr + expr


forms (which lead to shift/reduce conflicts in yacc!)


As John notes, precedence rules are a quick way to fix these (or rephrase
the grammar).


Ben


---
Ben Elliston
bje@cygnus.com
--

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