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Two grammars, one XML

4+5

plus(4,5)

expr = left, op, right .

@left = number .

@right = number .

-number = ["0"-"9"]+ .

@op = plus | minus .

-plus = "+" .

-minus = "-" .

expr = op,-"(",left,-",",right,-")" .

@left = number .

@right = number .

-number = ["0"-"9"]+ .

@op = plus | minus .

-plus = -"plus", +"+" .

-minus = -"minus", +"-" .

<expr left="4" op="+" right="5"/>