From: Tom Lane <tgl@sss.pgh.pa.us>
To: Corey Huinker <corey.huinker@gmail.com>
cc: Fabien COELHO <coelho@cri.ensmp.fr>,
        Daniel Verite <daniel@manitou-mail.org>,
        "David G. Johnston" <david.g.johnston@gmail.com>,
        Greg Stark <stark@mit.edu>, Erik Rijkers <er@xs4all.nl>,
        Robert Haas <robertmhaas@gmail.com>,
        Jim Nasby <Jim.Nasby@bluetreble.com>,
        PostgreSQL <pgsql-hackers@postgresql.org>,
        pgsql-hackers-owner@postgresql.org
Subject: Re: \if, \elseif, \else, \endif (was Re: PSQL commands: \quit_if,
 \quit_unless)
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Comments: In-reply-to Corey Huinker <corey.huinker@gmail.com>
	message dated "Fri, 17 Mar 2017 12:56:00 -0400"
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Date: Fri, 17 Mar 2017 13:27:49 -0400
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Corey Huinker <corey.huinker@gmail.com> writes:
>> In the end, I suspect that teaching all the backslash commands to do
>> nothing after absorbing their arguments is likely to be the least messy
>> way to tackle this, even if it makes for a rather bulky patch.

> Perhaps, but just glancing at \connect makes me think that for some
> commands (present or future) the number of args might depend on the value
> of the first arg, and variable expansion-or-not, backtick execution-or-not
> could alter the number of apparent args on the line, like this:

> \set x 'arg1 arg2'

> \if false
>     \cmd_that_takes_exactly_two_args :x
> \endif

Yeah, throwing errors for bad arguments would also need to be suppressed.

			regards, tom lane


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