Re: Why LL(1) Parsers do not support left recursion?

>How would I guess which one is that?


The technique is called "controlled ambiguity" in the Dragon book. You can
read about it there. I leave the LL solution as an exercise for the
interested reader, as if there are any.


Hint 1: We want to associate the ELSE with the closest IF, so use the
production that consumes the ELSE sooner.


Hint 2: There are only 2 possibilities, try them both and see which one
works.


The grammar solution is quite clever. If it were not so redundant, and
solved a problem that actually exists, it would be useful.


Forget about yacc for a minute. Assume you were creating the parse table by
hand. When you got to the shift-reduce conflict, you would say "Oh, I
remember this one from my first year compiler course. I will use the shift
as the entry in the parse table". This is what yacc does automatically.


The SLK parser generator: http://home.earthlink.net/~slkpg/

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