Arc Forumnew | comments | leaders | submitlogin
1 point by zck 1982 days ago | link | parent

I'm only halfway through the presentation, but it's really interesting.

Some thoughts: the grouping in the let form seems interesting, but I worry that it'll just be more confusing: wrapping all the args of e.g. let (c.f. Arc's with) with a single set of parens is a recipe for disaster, and I'm wondering how that works with values that are themselves a function call work. Does this work:

  (let top (+ (- b)
              (- (expt b 2)
                 (* 4 a c)))
       bottom (* 2 a)
       (/ top bottom))
Possibly: you could only make the first body argument to let the first odd item in the arguments to let that has parens, and not simply the first item in the arguments that has parens, but that prevents this from being working code:

  (let a 7
       a)
At least, it'll do something unexpected. Either way, I don't see these grouping parens as too complicated to understand. I do see how it overloads the meaning of parentheses, but 1. I don't see that as a problem, and 2. you could simply say that curly braces are exclusively for grouping. Either way is more readable.

The grouping symbols are much harder to parse than parentheses. Parens are bigger than characters, and our brains can easily pick them out. A symbol can't be so easily found, especially when it is mixed in with other symbols.

I like the idea of making awesome developer tools, including highlighting, but not everyone uses the same tools. How long will there be before there's an Emacs mode for the language? A vim plugin? How many people won't use one of those, or the text editor distributed with the language? It'll be hard to post code online to arbitrary sites, as it won't be syntax highlighted. This will be especially hard if you're trying to show people how nice your language is: "here's some code, isn't it cool?" is an easier sell than "go here, then look at the code, then see that it's cool".

Implicit parens? That's insane! This is a parse error!?:

  {foo a b c}
That seems incredibly more readable than the "proper"

  {foo a b c
Anyway, I'm interested in what happens here. I'll have to watch the rest tomorrow.


2 points by rocketnia 1982 days ago | link

"The grouping symbols are much harder to parse than parentheses. Parens are bigger than characters, and our brains can easily pick them out. A symbol can't be so easily found, especially when it is mixed in with other symbols."

When I use grouping symbols, I choose symbols like "-" and ":" which skirt that issue. I've considered setting a language-wide policy to use these symbols exclusively for grouping, but I haven't yet designed a language where that policy would fit in. (It would fit into Arc or Scheme, for instance, but I didn't design those. :-p )

---

"you could only make the first body argument to let the first odd item in the arguments to let that has parens, and not simply the first item in the arguments that has parens, but that prevents this from being working code"

The technique I use in Lathe's 'xloop is to greedily consume variable-and-anything pairs from the body. This terminates either when there's a non-variable at an odd location, or when there aren't enough elements left to make a pair, whichever comes first.

On a more extreme note, I'd kinda like to see most binding happen in 'do. If a variable-and-anything pair appears in a (do ...) form, that binding should hold for the remainder of the form. I implement this in Lathe as 'lets.

---

"Implicit parens? That's insane!"

I don't get it either. :) But if the idea is to have a "there are only a few ways to write it"[1] approach to syntax, that would explain both the implicit paren enforcement and the mandatory four-space indent.

By the way, I think you might need to write your 'let example like this:

  let top (+  (- b
              -   (expt b 2
                  * 4 a c)
      ,bottom (* 2 a
      / top bottom
---

[1] I'm not quoting anyone here!

-----

1 point by akkartik 1982 days ago | link

I watched it all and submitted a comment at http://brianwill.net/blog/2012/02/07/animvs-lisp-for-people-... which will hopefully eventually get through moderation.

I got the sense that the unbalanced parens are just a pedagogical device (though I'm not sure they helped me understand it any better). I didn't actually see any code samples with unbalanced parens. The final factorial example still had balanced parens which would be parse errors according to his earlier slide.

Above all, I'm left with a frustration that there isn't code to play with so I can clarify my confusions on my own and not get held up by ambiguities in some presentation. This is a common complaint of mine. Why do people do this? Why are they so concerned with getting it right before they're willing to let the world see it? If you throw it out earlier, who knows, somebody might come and contribute earlier. I'm more motivated to contribute when something is half-baked. Once you've figured it all out, it hardly seems worthwhile :)

-----

1 point by rocketnia 1980 days ago | link

"This is a common complaint of mine. Why do people do this? Why are they so concerned with getting it right before they're willing to let the world see it? If you throw it out earlier, who knows, somebody might come and contribute earlier. I'm more motivated to contribute when something is half-baked. Once you've figured it all out, it hardly seems worthwhile :) "

This part of what you're saying could well be reasoning in favor of discussion before code. Coding is a process of developing ideas, but so is discussion. This person has let the world see their ideas in the form of a presentation, rather than obsessing over getting them "right" in the form of runnable code first.

Unless... you're not even asking for runnable code? Interesting. Are you asking for people to be comfortable enough to do public brain dumps of all their works-in-progress, regardless of how useful they expect them to be?

-----

1 point by akkartik 1979 days ago | link

No I want runnable code. But isn't all code somewhat runnable? Otherwise it wouldn't be code. Almost any project is runnable within a few hours.

Your argument assumes that the presentation is less work than code, but I don't think that's true. He's clearly put hours of effort into presentation, but there isn't enough for me to even be clear on what he's proposing. Code would be unambiguously concrete in this respect. Even if it only works some of the time, if it has bugs, etc. I'd be able to get a sense of how it ought to work.

-----

1 point by rocketnia 1979 days ago | link

"Almost any project is runnable within a few hours."

"Your argument assumes that the presentation is less work than code, but I don't think that's true."

I take this a little personally, because there are many projects where I still don't even know what I want several years in. :) Well, programming is all about knowing what one wants, but I mean I don't even know these projects well enough to identify the core program I should start with. But I like to think I thrive on these ideas, because interesting big projects are the main reason I even give a second thought to little one-day projects.

Also, programming has a skill aspect to it. Unless someone's used a certain tool or technique before, it can be frustrating and intimidating. I personally find several things frustrating that others take for granted, like Emacs, Vim, manual memory management, the command line, and yes, riding a bicycle. :-p If someone's not ready to code up even a hackish language yet, I can relate.

-----

1 point by akkartik 1979 days ago | link

I certainly didn't mean to make it personal. I didn't even think I was talking about you.

I vaguely sense that we're using very different meanings for words like "runnable", "less work", "program", "project" and "right". But now I'm afraid to pick at this further.

I'm not claiming there should be no discussion without code, or that people must have working code when making a proposal, or anything nearly that strong. In this case from the certainty and polish of the presentation I assumed he knows what he wants. And he's referred to code so we know it's not a pure spec. So the bottleneck seems to lie in me understanding his proposal. And I was suggesting that sharing whatever code he has might help me over that hump. Showing code can only ever help, never hurt.

-----

2 points by rocketnia 1979 days ago | link

"I certainly didn't mean to make it personal. I didn't even think I was talking about you. [...] now I'm afraid to pick at this further."

Oh, sorry. I'm personally invested in this topic, but I'm not offended. But come to think of it, my post was a few claims fluffed up with personal foibles in place of other justification, and thanks for not being eager to refute the acceptableness of my foibles. :-p

---

"In this case..."

I don't have much of an opinion in this particular case. I was spurred on by the "common complaint" that people don't share their code in progress, and I'm interested in what kind of overall strategy we should pursue in response.

- Social networks for code sharing (e.g. package managers, HTTP, GitHub)?

- Collaborative development of large-scale online worlds (e.g. Wikipedia)?

- Socially encouraging or discouraging people to program depending on their personality?

- Investigating what kinds of programming problems are so mathematically exotic that meaningful code is exactly the thing that's hardest to develop?

- Different laws and licenses related to sharing code?

---

"And he's referred to code so we know it's not a pure spec."

I don't remember that part. I did skip a few boring parts in the video. ^_^;;

Hmm, maybe I even consider runnable code to be relatively boring and forgettable. XD; Probably depends on whether it's a product I'm eager to use right away. ^_^

-----

1 point by akkartik 1979 days ago | link

Socially encouraging or discouraging people to program depending on their personality?

Yeah, my hypothesis is that it's a psychological thing. Putting something out there is scary.

But this guy is putting out stuff, just not code. So my theory breaks down there :/ Never mind, let me just invite him over: http://brianwill.net/blog/2012/02/07/animvs-lisp-for-people-...

-----

1 point by Pauan 1982 days ago | link

"Possibly: you could only make the first body argument to let the first odd item in the arguments to let that has parens, and not simply the first item in the arguments that has parens, but that prevents this from being working code:"

There's actually a very sane way of handling this... You just say that "let" has only a single body expression, so as soon as you find a mismatched pair, that must be the body. That's what my language does with "$lets":

  $lets: a 1
         b 2
         c 3
    foo bar
The above is equivalent to this Arc code:

  (withs (a 1
          b 2
          c 3)
    (foo bar))
If you want to have multiple expressions in the body, you just use "$do":

  $lets: a 1
         b 2
         c 3
    $do: foo bar
         qux corge
This is like how Arc requires "do" if you want to evaluate multiple expressions in an "if".

---

In any case, I have to agree with you. The syntax rules seem somewhat convoluted and confusing. Naturally I'm biased, but I prefer the way my language handles the situation: it has very few parens, but it does so in a much more flexible, and I believe simpler way. I've put quite a bit of work into making the syntax work well, and will continue to do so.

-----

2 points by Pauan 1982 days ago | link

By the way... certain user conventions in my language mostly obviate the need for the syntax highlighting scheme that he came up with. In my language:

  1. Vaus are prefixed with $ (like in Kernel)
  2. Predicates end with ? (like in Kernel)
  3. Non-referentially-transparent things end with ! (similar to Kernel)
  4. Local variables start with a capital letter (like in Shen)
These rules combined means that it's trivial to write a syntax highlighter for my language, and it means the information is available even if you don't have syntax highlighting. To demonstrate, here's a 1-to-1 translation of the "factorial" function (shown in the video) into my language:

  $def factorial; N ->
    $loop: Cnt  N
           Acc  1
      $if: is? Cnt 0
        Acc
        $recur; --Cnt; Acc * Cnt
Naturally I wouldn't define it that way in my language, but... you get the idea.

Certainly there are some nice ideas in there, like giving special colors to external variables and such forth... but I think languages should look nice and be usable even without any syntax highlighting at all, with syntax highlighting as just an extra convenience, nothing more.

---

By the way... here's the idiomatic way to write "fact" in my language:

  $def fact
    0 -> 1
    X -> X * (fact X - 1)
Inefficient (because it isn't tail recursive), but even so, it's simple. If you want a tail-recursive version...

  $def fact-acc
    0 Acc -> Acc
    X Acc -> fact-acc X - 1; X * Acc

  $def fact: X -> fact-acc X 1
Or maybe you want to be like Haskell[1] and define it as...

  $def fact: X -> sum 1; range 1 X; mul
---

* [1]: http://www.willamette.edu/~fruehr/haskell/evolution.html

-----

1 point by akkartik 1982 days ago | link

Here's the highlighting I currently use: http://imgur.com/UCaMZ

The colors on this machine aren't quite right, but it shows what I care about:

a) Comments since they're never evaluated

b) Literals since they eval to themselves

c) Parens and ssyntax -- mostly as delimiters, but with backquotes distinguished

Everything else is unhighlighted. If the language does its job I really shouldn't be thinking about whether something's a macro. And local variables ought to be the default, so why add a little salience to Every Single One?

---

Wart comes with the vim settings for this highlighting: http://github.com/akkartik/wart/blob/2e01126102/vimrc.vim. It's very smart about ssyntax. The colors really indicate precedence. Notice in the second statement how some colons are colored like ssyntax, but not others. Or how the exclamation in mac! at the bottom isn't colored like ssyntax.

But after all that I don't want to make too many assumptions about how a new reader will view one's code. It needs to be visually balanced even without highlighting. Your typography rules remind me a little of early wart. See the if macro at the end of http://www.arclanguage.org/item?id=15137 -- and your comment on http://www.arclanguage.org/item?id=15140 :)

(Here's how if looks today, for comparison: http://github.com/akkartik/wart/blob/2e01126102/033check.war...)

-----

2 points by Pauan 1982 days ago | link

"If the language does its job I really shouldn't be thinking about whether something's a macro."

This is the same argument we had before... it's just not true. Macros/vaus behave fundamentally different from functions, they are not the same thing. By making them stand out, it gives your eyes something to grab onto.

Humans are wonderfully good at noticing patterns, but only if there's enough information there to pattern match on. If you don't provide this information in the syntax, it adds additional mental overhead.

You now have to memorize whether something is a vau or not (for common things like $let this isn't a problem, but for things less commonly used it can be a pain). The same goes for locals: if it isn't apparent in the syntax whether a variable is local or not, you have to mentally scan up the scope chain every single time you glance at code.

One of the problems with Lisp is that due to its lack of syntax, there's very few patterns that your mind can pick up on, so you have to do a full-blown mental parse of the source code just to determine whether something is a local or a vau or whatever.

It might not seem like much, but all the tiny extra mental overheads do add up. I believe that once you get used to my syntax, it's easier to read source code, because just by glancing at it your mind can notice all the little patterns.

Of course, there might be better criteria other than fn/vau/global/local/predicate/mutation... if so, I'd be interested in hearing it[1]. But I do think, whatever criteria you choose, it's important to have it be visually apparent so our poor human brains don't have to work so hard to parse our code. We are visual creatures, let's give our minds some visual feedback to chew on.

---

"And local variables ought to be the default, so why add a little salience to Every Single One?"

You forget that most functions/vaus are global. In fact, in my language, roughly 1/2 of the variables are globals, with the other 1/2 being locals. Out of those globals, roughly 1/3 are vaus, with the other 2/3 being fns.

---

"and your comment on http://www.arclanguage.org/item?id=15140 :)"

You're right, there is a fine line between adding syntax to make the source code more readable, and adding syntax so it ends up looking like Perl. I've tried to add in syntax only when I feel there's a significant benefit from doing so.

I'll note that my language doesn't have that particular problem mentioned in that particular post because my language doesn't have quasiquote/unquote/unquote-splicing, so that example would just be `@Body`

---

By the way, I used to be really off-put by how Kernel uses `$?!` in symbols to give them special meaning, and I also really disliked how Shen has local variables start with a capital letter... but after trying it out for a while, I got used to it and found that it actually wasn't that bad after all. Now I think it's an overall net win.

---

For comparison, here's how my syntax highlighting for my language currently looks:

http://img684.imageshack.us/img684/7873/screenshot0712201209...

---

* [1]: In particular, I just realized that it might be better to use $ for constructs that introduce additional binding names. This might be more useful than a general vau/fn distinction.

Then again, after looking through the source code, there were only a handful of vaus that didn't introduce new bindings: and, catch, hook, if, or, and quote

So, given how most vaus apparently exist for name binding, I think it's best to just use the general vau/fn distinction.

-----

1 point by akkartik 1981 days ago | link

"Macros/vaus behave fundamentally different from functions, they are not the same thing. ..it adds additional mental overhead."

Functions, macros, they're just ways to get certain behavior in the most readable way possible. Perhaps they add mental overhead in kernel because it's concerned about hygiene and such abstract matters.

Wanting to track your macros is OCD like wanting to avoid namespace pollution is OCD. Just relax, use what you need, remove what you don't need, and the function/macro distinction will fade into the background.

I guess we have to agree to disagree :)

-----

3 points by Pauan 1981 days ago | link

"Functions, macros, they're just ways to get certain behavior in the most readable way possible."

Sure. And their behavior is different: macros/vaus don't evaluate their arguments, functions do. That's because they're used for different purposes, so distinguishing between them is important and/or useful.

---

"Perhaps they add mental overhead in kernel because it's concerned about hygiene and such abstract matters."

I don't see what hygiene has to do with it... we're discussing about making it easy to tell at a glance whether a particular variable is a function or a vau, that's all. That's true regardless of whether the vau is hygienic or not.

I'll also note that I have not actually programmed in Kernel, so all my talk about "mental overhead" is actually referring to Arc, which is a distinctly unhygienic language.

In any case, my gut says that making a distinction between vaus and functions is important, so that's what I'm doing.

---

"Wanting to track your macros is OCD like wanting to avoid namespace pollution is OCD. Just relax, use what you need, remove what you don't need, and the function/macro distinction will fade into the background."

I do indeed worry about namespaces, which is why my language is going to have fantastic namespace support, most likely built on top of first-class environments.

Not only does this allow people to write solid libraries that don't need to worry about collisions, but it also has the massively major benefit that you know exactly what a variable refers to, because each module can be studied in isolation. You can't do that when everything is in one namespace.

So this has the same benefits that lexical scope and referential transparency give you: you can study different subparts of the system in isolation without worrying about what another part is doing.

Incidentally, that's why dynamic scope is so bad: it's not enough to understand what a single function is doing, you also need to understand what the rest of the program is doing, because some other random part of the program might change the dynamic variable.

That's why "lexical by default, marking certain variables as dynamic" is superior to "dynamic by default": it increases locality because you don't need to jump around everywhere trying to figure out what everything does, you can just focus on one part of the system at a time.

That's the whole point of functional programming, and my language is intentionally designed as a functional language. In fact, I plan for all the built-in data types to be immutable as well, for the exact same reasons. This should also help immensely with concurrency, similar to Clojure.

---

"I guess we have to agree to disagree :)"

I guess so.

-----

1 point by akkartik 1981 days ago | link

"I'll also note that I have not actually programmed in Kernel, so all my talk about "mental overhead" is actually referring to Arc, which is a distinctly unhygienic language."

That is really interesting, that our respective experiences are so different.

I'm with you on "lexical by default" -- I'm not totally crazy :) But the simplest possible mechanism that provides the similar advantages of namespaces is to just warn when a variable conflict is detected, when a global is defined for a second time.

I'm trying hard to introspect here, and I think the difference between lexical scope and namespaces for me is that when I'm programming by myself I don't need a second namespace, but I do still find dynamic scope to be error-prone. My entire belief system stems from that, that one should program as if one was working alone. Everything that helps that is good, anything that isn't needed is chaff.

-----

1 point by akkartik 1982 days ago | link

I like the highlighting; the color makes the typography less jarring. But you're right, it's one of those things one should familiarize oneself with before judging.

-----

1 point by akkartik 1982 days ago | link

Infix?! I'm curious to see how that translates to sexps.

-----

2 points by Pauan 1982 days ago | link

Oh it's very simple. The operators + - * / < > <= >= are the only infix operators (for now). They have the usual precedence rules that other languages use.

How they work is, they take one expression on the left, and one expression on the right, and then wrap em in a list, so that `X + Y` becomes `(add X Y)`, and then "add" is the actual add function.

So they're just syntax sugar for common infix operations, that's all. That's why the last example passed "mul" to "sum" rather than "*".

-----

2 points by akkartik 1982 days ago | link

"I'm wondering how let works with values that are themselves a function call."

Yeah. Or how about destructuring? Though he seems to prefer delimiters to structured lists. That seems wrong-headed as well.

-----