Re: [HACKERS] \if, \elseif, \else, \endif (was Re: PSQL commands:\quit_if, \quit_unless)

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От	Corey Huinker
Тема	Re: [HACKERS] \if, \elseif, \else, \endif (was Re: PSQL commands:\quit_if, \quit_unless)
Дата	23 февраля 2017 г. 02:15:01
Msg-id	CADkLM=dqO2G9yLtDB9PdJqyySau+EYFS1ypK5SSthya7yLEg2w@mail.gmail.com обсуждение исходный текст
Ответ на	Re: [HACKERS] \if, \elseif, \else, \endif (was Re: PSQL commands: \quit_if, \quit_unless) (Tom Lane <tgl@sss.pgh.pa.us>)
Ответы	Re: [HACKERS] \if, \elseif, \else, \endif (was Re: PSQL commands:\quit_if, \quit_unless)
Список	pgsql-hackers

Дерево обсуждения

On Wed, Feb 22, 2017 at 5:59 PM, Tom Lane <tgl@sss.pgh.pa.us> wrote:

Ah, I see why *that* wants to know about it ... I think. I suppose you're
arguing that variable expansion shouldn't be able to insert, say, an \else
in a non-active branch? Maybe, but if it can insert an \else in an active
branch, then why not non-active too? Seems a bit inconsistent.

The major reason was avoiding situations like what Daniel showed: where value of a variable that is meaningless/undefined in the current false-block context gets expanded anyway, and thus code inside a false block has effects outside of that block. Granted, his example was contrived. I'm open to removing that feature and seeing what breaks in the test cases.

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Re: [HACKERS] \if, \elseif, \else, \endif (was Re: PSQL commands:\quit_if, \quit_unless)