[Xapian-tickets] [Xapian] #760: Use lemon %fallback?

[Xapian]

#760: Use lemon %fallback?
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        Reporter:  olly         |      Owner:  olly
            Type:  defect       |     Status:  new
        Priority:  normal       |  Milestone:
       Component:  QueryParser  |    Version:  git master
        Severity:  normal       |   Keywords:
      Blocked By:               |   Blocking:
Operating System:  All          |
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 Recent versions of the lemon parser generator have a `%fallback`
 directive:

 https://www.sqlite.org/src/doc/trunk/doc/lemon.html#pfallback

 This is potentially useful for handling parsing of operators like `AND`,
 `OR`, `NEAR`, etc while also allowing parsing of pasted text which might
 contain these operators as words (especially an issue when
 `FLAG_BOOLEAN_ANY_CASE` is used and `and`, `or`, `near`, etc are
 recognised as operators).

 One wrinkle is that it would be useful to hook in and detect when this has
 happened so we can provide correction suggestions instead, or say the
 correction has been done but provide a way to undo it.  Maybe that can be
 done by using an intermediate token as the target for `%fallback` which
 records the correction that was done?

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Ticket URL: <https://trac.xapian.org/ticket/760>
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