Parser combinator "exception" operator

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Scala's parser combinator library doesn't have an analogue to the
EVNF "except symbol" - from the ISO standard for EBNF (14977), where

p - q

accepts if the left hand side accepts and the right hand side rejects.

Adding support for it would make it easier to translate EBNF notation
directly into parser combinators. As far as I can tell, this would be
simple, as:

p - q == not(q) ~> p

A proposed patch against r15798 is attached.

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Imported From: https://issues.scala-lang.org/browse/SI-1229?orig=1
Reporter: Aaron Harnly (aaronharnly)
Attachments:

• except-operator-patch.diff (created on Aug 15, 2008 3:39:05 PM UTC, 1234 bytes)

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@SethTisue said:
The parser combinators library is now community-maintained. Issues with it are now tracked at scala/scala-parser-combinators#61 instead of here in the Scala JIRA.

Interested community members: if you consider this issue significant, feel free to open a new issue for it on GitHub, with links in both directions.