http://www.perlmonks.org?node_id=169940


in reply to Eliminating Left Recursion in Parse::RecDescent

all this does is change the expression to expr : term '+' term | term which works fine but does not solve the problem. (a+b) + (c+d) etc.
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Re: Eliminating Left Recursion in Parse::RecDescent
by Abigail-II (Bishop) on May 29, 2002 at 10:42 UTC
    all this does is change the expression to
    expr : term '+' term | term
    which works fine but does not solve the problem. (a+b) + (c+d)

    That is because demerphq applied the rule wrongly. After applying the rule, we should get: 

        expr      :     term expr_tail
    expr_tail : '+' term expr_tail | {1}

    [download]

    Abigail

[reply]
[d/l]
      Doh. Yes. I did too. And you guys are the first to spot the error as well.

      In my defence, I got it right in one part, here 

      A : y R
R : x R | e

      [download]
      But omitted the R element in the example.

      I have updated the node. Thanks for your hawklike eyes.

      Yves / DeMerphq
      ---
      Writing a good benchmark isnt as easy as it might look.

[reply]
[d/l]

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