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

On Fri, Mar 24, 2017 at 4:10 PM, Fabien COELHO <coelho@cri.ensmp.fr> wrote:

>
> Hello Corey,
>
> I wished for the same thing, happy to use one if it is made known to me.
>> I pulled that pattern from somewhere else in the code, and given that the
>> max number of args for a command is around 4, I'm not too worried about
>> scaling.
>>
>
> If there are expressions one day like pgbench, the number of arguments
> becomes arbitrary. Have you looked at PQExpBuffer?


I will look into it.


>
>>> There seems to be pattern repetition for _ev _ef and _sf _sv. Would it
>>> make sense to create a function instead of keeping the initial
>>> copy-paste?
>>>
>>
>> Yes, and a few things like that, but I wanted this patch to keep as much
>> code as-is as possible.
>>
>
> If you put the generic function at the same place, one would be more or
> less kept and the other would be just removed?


> "git diff --patience -w" gives a rather convenient output for looking at
> the patch.


Good to know about that option.

As for a function for digested ignored slash options, it seems like I can
disregard the true/false value of the "semicolon" parameter. Is that
correct?


> I would suggest to put together all if-related backslash command, so that
>>> the stack management is all in one function instead of 4.
>>>
>>
>> I recognize the urge to group them together, but would there be any actual
>> code sharing between them? Wouldn't I be either re-checking the string
>> "cmd" again, or otherwise setting an enum that I immediately re-check
>> inside the all_branching_commands() function?
>>
>
> I do not see that as a significant issue, especially compared to the
> benefit of having the automaton transition management in a single place.


I'm still struggling to see how this would add any clarity to the code
beyond what I can achieve by clustering the
exec_command_(if/elif/else/endif) near one another.