| From: | Corey Huinker <corey(dot)huinker(at)gmail(dot)com> |
|---|---|
| To: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
| Cc: | Fabien COELHO <coelho(at)cri(dot)ensmp(dot)fr>, Greg Stark <stark(at)mit(dot)edu>, Erik Rijkers <er(at)xs4all(dot)nl>, Robert Haas <robertmhaas(at)gmail(dot)com>, Daniel Verite <daniel(at)manitou-mail(dot)org>, Jim Nasby <Jim(dot)Nasby(at)bluetreble(dot)com>, PostgreSQL <pgsql-hackers(at)postgresql(dot)org>, pgsql-hackers-owner(at)postgresql(dot)org |
| Subject: | Re: \if, \elseif, \else, \endif (was Re: PSQL commands: \quit_if, \quit_unless) |
| Date: | 2017-02-22 23:15:01 |
| Message-ID: | CADkLM=dqO2G9yLtDB9PdJqyySau+EYFS1ypK5SSthya7yLEg2w@mail.gmail.com |
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| Lists: | pgsql-hackers |
On Wed, Feb 22, 2017 at 5:59 PM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)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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