I don't know what the OP is requesting, but two major applications of this sort of technique would be database queries and message filtering, both according to user-supplied (or larger application configurable) criteria.

[For caveats re: 'user' and 'database', see my reply to dragonchild below.]

For example, SpamAssassin is basically a big user-criteria engine: it consults a list of user-supplied criteria and tallies a score total of matching ones, for each e-mail it inspects.

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[ e d @ h a l l e y . c c ]

In reply to Re: Re: Parsing conditional expressions by halley
in thread Parsing conditional expressions by Lorand

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