See Re: Left-associative binary operators in Parse::RecDescent for my preferred technique of doing precedence in grammars (stratification). You have one layer (stratum) for each precedence levels. Your grammar's starting rule is at the lowest precedence and the subrules increase in precedence. Finally, at the bottom level (of highest precedence), you have the rule for parenthesized expressions which recurses back to the top level (of lowest precedence). But this is unambiguous, because of the parentheses in this recursion rule.

P::RD may have other bells & whistles to help with precedence, but this is the only way I can ever remember to do precedence correctly, and it works with any kind of parser (although you may have to factor out left-recursion in right-associative operators).

Update: BTW, you can string together all operations of the same precedence level, which is probably more efficient. I.e, parse (a+b)*c*d*e*(f+g) into a shallow parse tree whose root has 5 children, instead of having a deeper parse tree whose nodes always have 2 children. However, for simplicity/uniformity it's often nice to always know that each node of the parse tree is a simple binary operation.

blokhead

In reply to Re: Order of Precedence in Parse::RecDescent grammar by blokhead
in thread Order of Precedence in Parse::RecDescent grammar by suaveant

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