Horton

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

Fabien COELHO <coelho@cri.ensmp.fr>

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From: Fabien COELHO <coelho@cri.ensmp.fr>
To: Corey Huinker <corey.huinker@gmail.com>
Cc: Robert Haas <robertmhaas@gmail.com>, Erik Rijkers <er@xs4all.nl>, Tom Lane <tgl@sss.pgh.pa.us>, Daniel Verite <daniel@manitou-mail.org>, Jim Nasby <Jim.Nasby@bluetreble.com>, PostgreSQL <pgsql-hackers@postgresql.org>, pgsql-hackers-owner@postgresql.org
Date: 2017-02-14T10:22:57Z
Lists: pgsql-hackers 
>> For two states:
>>   * for being executed (beware, it is ***important***)
>
> It does lend importance, but that's also the line continuation marker for
> "comment". Would that be a problem?

Argh. Indeed, even if people seldom type C comments in psql interactive 
mode...

Remaining ASCII characters I can thing of, hopefully avoiding already used 
ones: +%,@$\`|&:;_

So, maybe consider these ones:
   "+" for it is "on"
   "`" which is a "sub-shell execution"
   "&" for "and the next command is ..."

>>   / for not (under the hood, and it is opposed to *)
>
> +1, I was going to suggest '/' for a false state, with two possible
>     metaphors to justify it
>  1. the slash in a "no" sign ("no smoking", ghostbusters, etc)
>  2. the leading char of a c/java/javascript comment (what is written here
>     is just words, not code)

Great.

-- 
Fabien.

Commits

  1. Support \if ... \elif ... \else ... \endif in psql scripting.

  2. Add a "void *" passthrough pointer for psqlscan.l's callback functions.