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From: | Evan Lavelle |
Subject: | Re: shift/reduce conflict with unary |
Date: | Wed, 22 Aug 2007 12:44:21 +0100 |
User-agent: | Thunderbird 2.0.0.6 (Windows/20070728) |
"5 6 +4"How do you expect this to be scanned? Does it contain 3 summation_expressions ("5", "6", "+4") or 2 ("5", "6+4")? There's an ambiguity - you haven't defined an expression list in an unambiguuous way.
this is a very common problem - how do you define a list of something complex? Can you define expression lists to require a separator? How about
"5, 6, +4" -> 3 expressions "5, 6 +4" -> 2 expressions
Is it okay if I disregard the conflict if the grammar works anyway?
I personally think that this is a mistake, but it is commonly done. The problems are that you may not understand why there is a conflict in the first place, and any subsequent maintainers certainly won't understand; I prefer to try to remove the conflict.
Evan
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