Re: [PATCH] Support the mksh's ${|func;} substitution

[Sebastian Gniazdowski <sgniazdowski@xxxxxxxxx>]

I thought that I ask: should I continue working on the feature? I.e.
does it have a chance of being accepted?

The feature would be: a new substitution flag (x for execute, or | to
mark similarity to mksh's ${|code;}) that would execute the provided
code and substitute the value of $REPLY. E.g.:

- var='REPLY=test'; echo ${(x)var} -> test
- echo ${(x):-REPLY=test2} -> test2
- noglob print -rl ${(x):-for val (test test3) {
REPLY=\$val
}}
-> test3

The usefulness is the ability to map code onto array elements (with
(#m) or (#b) flags) and general lambda-like use-case.


On Sat, 7 Sep 2019 at 23:19, Sebastian Gniazdowski
<sgniazdowski@xxxxxxxxx> wrote:
>
> On Sat, 7 Sep 2019 at 22:19, Stephane Chazelas
> <stephane.chazelas@xxxxxxxxx> wrote:
> >
> > 2019-09-07 20:09:57 +0200, Sebastian Gniazdowski:
> > > The parsing would have to be changed to prevent the "=" in function names?
> > [...]
> >
> > No, I meant that you'd need the parser to handle that case of a
> > pseudo-command group  (a {any shell code here} but with {|
> > instead of {)).
> >
> > So you can do:
> >
> > echo ${|
> >   whatever $(...)
> >   for i do
> >     ...
> >   done}
> >
> > Whether it would actually be difficult or not I can't comment,
> > I've not looked at the parser code.
>
> I think that it's already supported with the single exception that }
> would have to be quoted:
>
> % print ${|
>   whatever $(...)
>   for i do
>     ...
>   done;}
> zsh: no such function: \n  whatever $(...)\n  for i do\n    ...\n  done
>
> > Having an operator that *only* invokes a function to do an
> > expansion is less useful IMO. That just sound like a very
> > limited form of command substitution where you could have done a
> > more complete form by allowing any code instead of just one
> > function invocation without argument.
>
> Ok, I agree, the lambda-function reminiscent version is better. It
> also isn't much harder to implement – instead of the doshfunc() just
> bin_eval() would have to be called. I attach such patch. However, it
> has some problems:
>
> arr=( val1 val2 abc1 abc3 )
> print ${arr[@]//(#b)(*)/${|REPLY\=test;}}
> Output:test test test test
>
> So the = has to be quoted. Also, not much more works. REPLY\=$MATCH
> nor REPLY\=\$MATCH are working. I wonder why, as it doesn't look that
> bad in general:
>
> whatever() { echo func ran; }
> echo ${|
>   whatever $(...)
>   for i in a b c; do
>     REPLY\=1
>   done;}
>
> Output:
> func ran
> 1
>
> --
> Sebastian Gniazdowski
> News: https://twitter.com/ZdharmaI
> IRC: https://kiwiirc.com/client/chat.freenode.net:+6697/#zplugin
> Blog: http://zdharma.org



--
Sebastian Gniazdowski
News: https://twitter.com/ZdharmaI
IRC: https://kiwiirc.com/client/chat.freenode.net:+6697/#zplugin
Blog: http://zdharma.org