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3 points by absz 5622 days ago | link | parent

[This is about your "quest for the ideal each", not about defined.]

Not to be a heretic, but this is where a more complex syntax shines. Or even something à la CL's loop, where you have a fixed keyword argument:

  (every x in '(1 2 3)
    (prn x))

  ; equivalent to
  
  (every '(1 2 3)
    (prn _))
Lightly tested:

  (mac every args
    (if (and (>= (len args) 3) (is args.1 'in))
      `(each ,(car args) ,(car:cddr args)
         ,@(cdr:cddr args))
      `(each _ ,(car args)
         ,@(cdr args))))
Another option would be anaphoric each:

  (mac aeach (xs . args)
    `(each it ,xs ,@args))
This produces

  (aeach '(1 2 3)
    (prn it))
It's not quite what you wanted, but it's similar. (It may also have been suggested before, I don't recall.)


2 points by palsecam 5622 days ago | link

Your 'every example is very very attractive. I think I'll adopt it at this point:

1. It does the job without problematic cases, like there would be in what I describe:

   (with (lst '(1 2 3)
          v 3)
      [...]
      (myidealeach v lst (prn v)))  ; <-- v mistaken for the seq to traverse here, 
                                    ; because it is defined
2. OK, it adds some syntax and this is bad, but for the common case where I'd like an implicit '_ variable, it's as short as possible!

3. For the other cases, the extra "in" is not so heavy, and in a way it makes the expression more readable!

Thanks a lot absz!

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For the rest:

> anaphoric each

Yes, a good idea but I don't like to have two loop constructs where one could suffise. Currently, I'm using something like that (I have a 'each_) but this sucks IMO.

However, interesting that you choose to use 'it' and not '_'. It makes me realize, maybe it would be better if there was only one of the 2, there are a bit redundant aren't they?

   (aif (car a) (prn _))  
   ; I like this, because "_" is more visible than "it", less likely 
   ; to be confused with a "normal" variable, and less english-centric
Or:

   ([* it it] 2)  ; hmmm don't like that so much actually
This is pure personal taste however.

In the same way, this is also personal taste, but I mention this because an American/British people may not think about this kind of stuff. I prefer "list?" over "alist" because anyone used to the latin alphabet will quickly understand what it does (and even this is not the majority of people...). True story, I didn't understand what "acons", "alist" mean when I first looked at Arc (I'm French), while the Scheme way to name predicates was obvious at first sight.

> CL's loop

Ouch I'd really not copy 'loop too much however.

In a way, it is a good construct, I mean it is very powerful, but I can never remember of the syntax to do basic things, and this is why I prefer the Arc way here. 'loop is really a DSL in itself.

Thanks again!

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2 points by absz 5621 days ago | link

Glad I could be of assistance :)

As for the it/_ question: I hadn't noticed until writing my post that _ and it (and self in afn) were serving similar purposes; I don't really know which one I like more, though that's not something I care heavily about. (My feeling about the English-centricity problem is that if everything else in the language is already in English---if, each, and, etc.---then changing it to _ probably wouldn't make a huge difference.)

As for the function-naming issue: I also prefer the Scheme naming convention, though not for multiple-language reasons (I'm an American [mais je peux parler Français]); that's an aspect I hadn't thought of. (The a-predicate versus anaphoric thing is already annoying.) Internationalization of programming languages is a hard problem that I don't think anybody's tried to tackle, and I'm not sure how tractable it is---it would be interesting to see a language or framework which tried to explore that design space. The obvious approach is something like

  (mac si (c v f) `(if ,c ,v ,f))
  (= chaque each)
  ; etc.
The downside is that this only internationalizes the core; any library still has to support these synonyms or have a translator, and so I'm not sure how big the eventual gain is. (I think AppleScript had this once, but since applications didn't support this, that feature died.)

In my opinion (and I've barely used CL), loop is a brilliant piece of code because it's a great little DSL for iteration; at the same time, also having simpler alternatives, e.g. each, available is really handy because that way you don't need to know everything loop can do all the time.

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2 points by palsecam 5621 days ago | link

> then changing it to _ probably wouldn't make a huge difference

I also don't think it would be a huge difference for non-english programmers, although it may be a little win. But for my case, I don't prefer "_" just because of that. I'd say, the main reason is that "_" is more easily recognized by my parser (aka brain) as a special variable than "it" because it is an uncommon glyph. "it" gets lost in the flow of the program.

> I'm an American [mais je peux parler Français]

Now, that is not common and that is cool. I mean, not that you know how to speak French, but that you know how to speak a foreign language.

Those who know no foreign language knows nothing of their mother tongue. -- Goethe

It's not a coincidence that Larry Wall (Perl creator) studied linguistics...

> that's an aspect I hadn't thought of

Well in this case I can go to sleep happy, knowing I made you aware of something new ;-)

> a-predicate versus anaphoric thing is already annoying.

Yes! When I realized 'acons & the like were predicates, well I thought 'afn was, too...

> loop is a brilliant piece of code because it's a great little DSL for iteration; at the same time, also having simpler alternatives, e.g. each, available is really handy

Totally agreed. 'loop is something great to have as a library or something, but if it's the only way you have to do basic iteration, well, it sucks IMO. Because in top of knowing CL you have to know the 'loop stuff, which is completely different. Gosh, writing this message I realize I don't even remember how to iterate over a list while printing its elements. But yes, 'loop is extremely powerful.

Anyway, thanks once again absz, your message was really interesting to read!

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