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Comment by kylec | Hacker News Reader

While I hear many people complaining about the "awkward" and "hard-to-read" syntax, it's rare to hear someone compliment the syntax of lisp. I am a big fan of the Lisp syntax because it's so simple and consistent - probably a relic of its roots in lambda calculus. Not having to worry about operator precedence is a huge bonus in itself - I don't know why on one hand people cling to PEMDAS, logic, assignment, etc having a complicated hierarchy of precedence and on the other reject lisp because it's too "foreign".

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Clarity and unambiguity aren't necessarily the same things. The human brain can handle huge amounts of ambiguity, and our spoken languages reflect this. A programming language is meant to be a bridge between our ambiguous thoughts and the unambiguous calculations of a computer. S-expressions constrain the format of the programmer's dialog with the computer, making it simple and monotonic. For some people this will add a new level of clarity to their work, but for other people it will just limit what they can easily express in code.

High-level languages like Ruby may contain lossy abstractions that obscure the low-level workings of the machine, but Lisp is another lossy abstraction that has the potential to obscure the high-level, abstruse workings of our own minds. Both of these abstractions can be valuable, but neither is without its shortcomings.

Bravo! People tend to boggle when I decry Lisp as being hopelessly low-level.

Sometimes ambiguity can be free, allowing indifference to how the machine works, without obscuring it at all. A good example is classical Hindley-Milner type inference (the algorithm that adds type annotations to plain System F code): it is fairly easy to construct oddball statements where annotating the types is undecidable or would cause resource exhaustion. But it turns out that for the known examples, it would be either impossible to decide the types in any form, or it would take O(c^n) bytes to enumerate the annotations.

So effectively there is no downside to the ambiguity -- the ambiguous statements are already infeasible for other reasons. Everybody Wins!

People tend to boggle when I decry Lisp as being hopelessly low-level.

Intriguing. I'm not really convinced by your example though. In the spirit of conciseness is power[1], can you provide a short program that should be formally expressible in a good enough language, but isn't concisely in Lisp?

Or maybe your definition of low-level is different from mine?

[1] That's the PG version, of course.

I don't buy that concision is power. This borders on a tautology, but expressiveness is power. Concision is part of that (a big part, even), but it's not everything.

My only problem with Lisp is that it's exactly the sum of its parts - no more, no less. Everything decomposes into self-similar pieces, which decompose into other pieces, and on and on, turtles almost all the way down. This is wonderfully elegant, but also feels like it precludes creating something which is more than the sum of its parts. This may not seem like a problem to a lot of people, or just sound like self-important nonsense, but the thing I enjoy most about programming is the tangible sense of gestalt you get when you've been working on a codebase for long enough. For me, Lisp doesn't provide that.

>I don't buy that concision is power. This borders on a tautology, but expressiveness is power. Concision is part of that (a big part, even), but it's not everything.

Yeah, I completely agree. I was going to write about it, but then figured it wasn't relevant to the question.

I'd love to discuss these old PG essays one day.

I'd like to understand what you mean. Is there a way you could provide an illustrative example?

You have an interesting point here that is not often discussed.

I am pretty new to programming, which means that I'm not stuck in conventions about how code syntax is supposed to be. On this background I find lisp pretty easy exactly because the syntax is so simple.

To me lisp is like chess: It's easy to grasp the basic rules, but hard to become a master.

Then Scheme is like Go. Interesting like Common Lisp, but more beautiful.

I once scribbled down some Scheme on a napkin during a conversion with my sister, a non-programmer. (God knows how it came up, but anyway, it did.) She looked at it, and said two things:

1. So many parentheses!

2. You made a mistake right here.

I agree. I wish ML used s-expressions.

Also, you might like this presentation, "The Swine Before Perl" by Shriram Krishnamurthi (of PLT). It's a great thing to show people who wonder how you could think Lisp has a good syntax: http://www.cs.brown.edu/~sk/Publications/Talks/SwineBeforePe...

(Also: SK's book is great.)

ML and it's successors do not want for s-exprs.

They force an inappropriate fundamental data type on everything, and are only of benefit if you want to fiddle with the insides of extant functions.

Use composition like a real FPer. Learn that there's so much more to data than lists + atoms.

> They force an inappropriate fundamental data type on everything, and are only of benefit if you want to fiddle with the insides of extant functions.

Please explain.

(And I know composition, etc. I also use Haskell and Forth.)

I think what is meant is that the list is the primary data structure for everything in lisps. Fortunately, it is not the only data structure in lisps. I dislike constructs where eg. a graph edge is built as:

'(GRAPH-EDGE <source-vertex> <target-vertex>)

whereas in ML you would write

type edge = { source: Vertex.t; target: Vertex.t }

which is not a list, but an entirely different representation. In Common Lisp the representation could of course be a CLOS object or a DEFSTRUCT (I think, my CL-fu is definitely not that good).

As for the composition, lisps are lacking (nice) currying which is one of the basic building blocks when constructing combinator-libraries.

Ah, I misread it as that ML "force[s] an inappropriate fundamental data type on everything", not s-expressions.

It's true that earlier Lisp dialects had trouble. But in Common Lisp, you can do currying just fine. At work (ITA Software), it's part of our standard utility library.

Just read the slides.

The two comparing s-expressions ("ugly, evil, and an insidious plot hatched by misbegotten academics") and XML ("a hip, cool, great new idea") I found to be particularly brilliant.

I agree - I think the other strength of it is that macros are less messy then a language with infix operators/functions.

There is something nice about a language (lisp) that doesn't look like anything else, in an artistic sense (not sure if that counts for much).

I think when most people complain about the parens, they are really complaining about the endless ))))))) at the end of an expression.

Interlisp had the last part correct. [ was a special open paren and ] closed all open parens back to (and including) the most recent [.

Nice - I remember someone saying that that in emacs you could have it format it using indentation and now show the parens (or maybe it wasn't emacs).

It was Emacs: http://www.emacswiki.org/cgi-bin/wiki/UnParenMode

In practice, it's just not a problem, because your interactive development environment takes care of it for you. I think the idea that anyone should be expected to program by using something with the power of Microsoft Notepad is an obsolete view. GNU Emacs with Lisp mode makes it very easy to work with the parentheses.

Meanwhile, we have no "dangling else" problem. Also, we have no need to memorize C's 15 levels of operator precedence, so when you see an expression, you never have to puzzle over how the items are grouped. In simple cases of C expressions, of course, it's easy, but it can get complicated. See "Java Puzzlers" by Josh Bloch and Neal Gafter to see how C/Java-style syntax can get you into trouble and fool you. There are pros and cons to each approach (C/Java and Lisp). I've used all of them extensively, and I prefer the Lisp way.

I agree that it's not a problem, but for newcomers all that parenthesis accumulation is quite problematic. I speak out of my personal experience: I've abandoned lisp even before learning something about macros because I couln't stand the parenthesis. I gave a second chance to Lisp some time ago, years after my first attempt. I've walked through Seibel's book entirely and know I love Lisp, but the parenthesis give a really bad first impression, they only make sense after you get to know the language better.

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