Re: parser hacking: conditional fields
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- Subject: Re: parser hacking: conditional fields
- From: Miles Bader <miles@...>
- Date: 2013年3月01日 11:02:58 +0900
Miles Bader <miles@gnu.org> writes:
> Sven Olsen <sven2718@gmail.com> writes:
>> Thus my latest excursion into lparser.c. The idea is to allow ~ to denote
>> a "conditional field reference". When evaluating 'table~key', the result
>> is 'table.key' provided that 'table' exists. But if 'table' doesn't exist,
>> then 'table~key' evaluates to 'table'. I fall back on the nonexistent case
>> when 'table' equals nil or false, so the semantics match the behavior of
>> more standard 'and/or' tricks.
>
> Hmm, how about ".?" instead of "~" (which seems kind of random) ...?
> Using ".?", the meaning seems to almost jump out at you...
.. or "?.", and then similarly "?[...]" ?
-miles
--
"Yorton, Wressle, and Gospel Oak, the richness of your heritage is ended.
We shall not stop at you again; for Dr Beeching stops at nothing."