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2 points by vsingh 6154 days ago | link | parent

If you have found through long experience that Loop truly offers something unique that can't be offered as well (or as intelligibly) by a combination of simpler operators, then I'll have to take your opinion seriously.

I've made a thread to collect exemplary examples of Loop in action (http://arclanguage.org/item?id=2938) and it'd be great if you could contribute your favorites, e.g. from Cells or other code you've written.

Personally, I don't have the same experience as you. I've found Loop to be useful as a replacement for iteration constructs that should have been in CL to begin with, e.g. dovector, when I'm too lazy to code the requisite macro. I haven't ever had to use Loop in its full complexity.



4 points by kennytilton 6154 days ago | link

Sorry, it just sounds from what you have posted so far that you do not know CL's loop, by which I mean make an effort to use all of its capabilities such that you would know what's there so well that you had it at your fingertips. I am having the same problem with CL idiots denouncing Arc who probably have not even installed it.

You want me to code (dotimes (x 10) (foo))?! No way!

  (loop repeat 10 do (foo)).
And that is not even a good example!!

  (let (x)
     (dolist (y whatever (nreverse x))
        (let ((py (pfft y)))
           (when py
               (push (yo-mama (cons y py)) x)))
Egad! How about:

   (loop for y in whatever
         for py = (pfft y)
         when py collect (yo-mama (cons y py)))
Is the first version starting to look like a disassembly? Bingo!!! :)

btw, the thing that got me to break down and give loop a chance was learning that the expansion was highly optimized code, meaning (for example) it would not first map across whatever and then delete the nils.

but these examples still do not get to the point of LOOP being a DSL. That property emerges only in the next level of application, as even the loop form expands to ten lines. But once you have loop under your belt (I kill myself) you do not even want to code a simple dotimes, that bogus unused count variable just pisses you off no end, never mind all the extra (wait for it) parentheses!

pg, phone home, all is forgiven! :)

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2 points by vsingh 6153 days ago | link

That looks interesting. I've submitted that example to my thread.

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