Re: if-then-else ambiguity

Duncan Smith <>
18 Apr 1997 01:33:42 -0400

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Related articles
if-then-else ambiguity (Umm) (1997-04-16)
Re: if-then-else ambiguity (Duncan Smith) (1997-04-18)
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From: Duncan Smith <>
Newsgroups: comp.compilers
Date: 18 Apr 1997 01:33:42 -0400
Organization: Flavors Technology, Inc.
References: 97-04-072
Keywords: yacc, parse

Umm wrote:
> Would it be a correct way, of solving a shift reduce problem in
> yacc/bison of the if-then-else by defining a %left precedence (the
> biggest one) to the else?? that way, we are sure (we were already but
> at least there will not be a warning) that in the presence of the
> else, it will be immediately reduced and not shifted, thus making it
> belong to the closest if.
> Is this correct??

I think the resolution must be to SHIFT. I believe this is the default

SHIFT leaves IF-THEN-ELSE on the stack which is then reduced.

REDUCE reduces the IF-THEN on the stack, leaving the ELSE as input to
match an Outer IF-THEN.


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