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bug#26338: 26.0.50; Collect all matches for REGEXP in current buffer


From: Philipp Stephani
Subject: bug#26338: 26.0.50; Collect all matches for REGEXP in current buffer
Date: Sat, 08 Apr 2017 14:41:29 +0000



Tino Calancha <address@hidden> schrieb am Sa., 8. Apr. 2017 um 15:42 Uhr:


On Sat, 8 Apr 2017, Philipp Stephani wrote:

>
>
> Tino Calancha <address@hidden> schrieb am Sa., 8. Apr. 2017 um 06:46 Uhr:
>
>
>       On Fri, 7 Apr 2017, Drew Adams wrote:
>
>       >>> Or an addition to cl-loop that would allow doing something like
>       >>>
>       >>>    (cl-loop for m being the matches of "foo\\|bar"
>       >>>             do ...)
>       >>>
>       >>> Then you could easily 'collect m' to get the list of matches if you want
>       >>> that.
>       >>
>       >> Your proposals looks nice to me ;-)
>       >
>       > (Caveat: I have not been following this thread.)
>       >
>       > I think that `cl-loop' should be as close to Common Lisp `loop'
>       > as we can reasonably make it.  We should _not_ be adding other
>       > features to it or changing its behavior away from what it is
>       > supposedly emulating.
>       >
>       > If you want, create a _different_ macro that is Emacs-specific,
>       > with whatever behavior you want.  Call it whatever you want
>       > that will not be confused with Common Lisp emulation.
>       >
>       > Please keep `cl-' for Common Lisp emulation.  We've already
>       > seen more than enough tampering with this - people adding
>       > their favorite thing to the `cl-' namespace.  Not good.
>       Drew, i respect your opinion; but so far the change
>       would just extend `cl-loop' which as you noticed has being already
>       extended before.
>       For instance, we have:
>       cl-loop for x being the overlays/buffers ...
>
>       Don't see a problem to have those things. 
>
>
> I do. They couple the idea of an iterable with a looping construct, and such coupling is bad for various reasons:
> - Coupling of unrelated entities is always an antipattern.
> - For N iterables and M looping constructs, you need to implement N*M integrations.
> Instead this should use an iterable, e.g. a generator function (iter-defun). cl-loop supports these out of the box.
Then, you don't like (as Drew, but for different reasons) that we have:
cl-loop for x being the buffers ...

I don't like it, but it's there and cannot be removed for compatibility reasons, so I'm not arguing about it. I'm arguing against adding more such one-off forms.
 

but it seems you are fine having iter-by clause in cl-loop, which seems an
Emacs extension (correctme if i am wrong).  So in principle, you are happy
with adding useful extensions to CL, not just keep it an emulation as
Drew wants.

Yes, I don't care about Common Lisp. The iter-by clause is less of a problem than 'buffers' etc. because it's not a one-off that couples a looping construct with some random semantics.
 

Your point is about performance.

No, I care mostly about clarity, simplicity, and good API design, including separation of concerns.
 
  I am driven by easy to write code.
Maybe you can provide an example about how to write those things using
the iter-by cl-loop clause.

Sure:
 (require 'generator)
(iter-defun re-matches (regexp)
  (while (re-search-forward regexp nil t)
    (iter-yield (match-string 0))))
(iter-do (m (re-matches (rx digit)))
  (print m))
(cl-loop for m iter-by (re-matches (rx digit))
do (print m))


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