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

Hello,

I'm looking forward to the doc update.

My 0.02€ about prompting:

>> Given that there is no more barking, then having some prompt indication
>> that the code is inside a conditional branch becomes more important, so
>> ISTM that there should be some plan to add it.
>
> Yeah, prompting just got more important. I see a few ways to go about this:
>
> 1. Add a new prompt type, either %T for true (heh, pun) or %Y for
> branching. It would print a string of chained 't' (branch is true), 'f'
> (branch is false), 'z' (branch already had its true section). The depth
> traversal would have a limit, say 3 levels deep, and if the tree goes more
> than that deep, then '...' would be printed in the stead of any deeper
> values. So the prompt would change through a  session like:
>
> command       prompt is now
> -----------   ---------------------------------------
> \echo bob     ''   = initial state, no branch going on at all
> \if yes       't' = inside a true branch
> \if no        'tf' = false inside a true
> \endif        't' = back to just the true branch
> \if yes       'tt'
> \if yes       'ttt'
> \if yes       '...ttt' = only show the last 3, but let it be known that
> there's at least one more'
> \else         '...ttz' = past the point of a true bit of this branch

I like the "tfz" idea. I'm not sure whether the up to 6 characters is a 
good, though.

> 2. The printing of #1 could be integrated into %R only in PROMPT_READY
> cases, either prepended or appended to the !/=/^, possibly separated by a :

Hmmm. Logically I would say prepend, but the default prompt is with the 
dbname, which is mostly letters, so it means adding a separator as well.

> 3. Like #2, but prepended/appended in all circumstances

I would say yes.

> 4. Keep %T (or %Y), and reflect the state of pset.active_branch within %R,
> a single t/f/z

Yep, but with a separator?

> 5. Like #4, but also printing the if-stack depth if > 1

Hmmm, not sure...

Based on the your ideas above, I would suggest the following:
  calvin=> \if true  calvin?t=> SELECT 1 +  calvin?t->   2;    3  calvin?t=> \if true  calvin?t=>   \echo hello
hello calvin?t=> \endif  calvin?t=> \else  calvin?z=>   \echo ignored  calvin?t=> \endif  calvin=>
 

Or maybe use "?.t" for the nested if...

-- 
Fabien