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


From: Tino Calancha
Subject: bug#26338: 26.0.50; Collect all matches for REGEXP in current buffer
Date: Sun, 9 Apr 2017 00:20:22 +0900 (JST)
User-agent: Alpine 2.20 (DEB 67 2015-01-07)



On Sat, 8 Apr 2017, Philipp Stephani wrote:



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.
I see.  Thanks for the clarification.
 

      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.
Some people like it and refer about that as the 'expressivity' of the loop facility. I guess it's a matter of taste, don't need to use such constructs if you don't like it. Some people do.
  

      Your point is about performance.


No, I care mostly about clarity, simplicity, and good API design, including 
separation of concerns.
Expressibity and readability might be some kind of clarity.
I totally agree about API design and 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))
Thank you very much for your examples.  They are nice.  I am not
as familiar as you with generators.  I must study them more.

Between A) and B), the second looks at least as simple and clear as
the first one, and probably more readable.

A)
(iter-defun re-matches (regexp)
  (while (re-search-forward regexp nil t)
    (iter-yield (match-string-no-properties 1))))

(cl-loop for m iter-by (re-matches "^(defun \\(\\S +\\)")
         collect m)

B)
(cl-loop for m the matches of "^(defun \\(\\S +\\)"
         collect m)

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