(How to Write a (Lisp) Interpreter (In Python)) (2010)

56 pointsposted 2 hours ago
by tosh
(norvig.com)

25 Comments

chombier

an hour ago

If you ever wondered how to write a programming language, this is probably the best resource to get started (and then of course Crafting Interpreters).

See also part 2 https://norvig.com/lispy2.html

zahlman

an hour ago

(how-to in-python (write (interpreter lisp)))

consumer451

42 minutes ago

Yes, but to be fair, you only have a couple minutes to fight the HN title regex.

azhenley

an hour ago

Writing a Lisp is one of my favorite projects. I try to do it every year or two, taking a different approach each time.

onraglanroad

38 minutes ago

The one where you replaced parentheses with the crying laughing emojis was definitely the worst.

timonoko

40 minutes ago

One of those exercises that are now just boring, because AI does it better.

Gemini did write Lisp-1 interpreter in Linux-assembly the other day. It was ready to implement garbage collection and compiler and all shit, but that was just depressing from human point of view.

genxy

16 minutes ago

There is always someone better than you at almost everything you do, this is statistical reality.

If all you care about is the artifact and not the path, there is no reason to do anything.

Use the tool to better yourself, your understanding and push the limits of what is possible. If a Lisp in assembly with GC is now hello world, change what a hard project is.

I see this attitude a lot, and I think it is rooted in a sort of self-centered elitism. Anyone can do it, so why do it? Instead you could have the AI teach you how to implement it yourself with a deep understanding that no human, even if you paid them, would put up with.

But sure, get depressed. But why tho?

tosh

27 minutes ago

is learning how to accomplish or understand something boring

just because someone or something else does it better?

Lyngbakr

15 minutes ago

It depends why you're doing it. Are you doing it for the product or the process? (Of course, they're not mutually exclusive.) I do it for the fun of building, in which case AI is irrelevant.

chamomeal

28 minutes ago

I mean it’s still worth doing, even if AI can do it. But I definitely empathize with that bit of AI ennui.

tosh

2 hours ago

I can't recommend highly enough to implement a simple lisp (or a forth).

Illuminating experience and it will also help you see (among many other things) the parentheses in a different light.

stdatomic

an hour ago

First day of paradigms course in the 2000s and prof says "if your opinion of Scheme is too many parentheses, then you're an idiot."

Needless to say that was my opinion and every day I think, more and more, how right he was.

(later I did make some gui apps that included scripting and chose s-expr syntax because of how simple it is to implement it)

bananaflag

an hour ago

There are two problems with Lisp parentheses in my opinion:

1) Humans are not that equipped to handle that level of nesting without some other aid, this is why Lisp code is usually indented.

2) Parentheses aren't just about grouping, and this is unintuitive. For example, x is not the same as (x). This is a bit like in set theory where x is not the same as {x}, but parentheses do not look like the kind of sign that would work like that.

NooneAtAll3

an hour ago

main problem isn't brackets themselves - it's that they're too on the right

had brackets been displayed as curly braces in C - everything would look much more manageable

eska

44 minutes ago

I changed my opinion about parens when I stopped formatting like C, and used indent rather than parens to denote blocks. That is, a large amount of them at the end is totally fine.

phpnode

an hour ago

so, instead of

    (foo (bar (1 2 3))
you'd prefer

    {
      foo {
        bar {
          1
          2
          3
        }
      }
    }
is that right?

RedCinnabar

20 minutes ago

Man these kind of resources have aged really bad in the age of AI.

Crespyl

15 minutes ago

Why would AI make these age worse than, say, libraries or languages becoming obsolete?

I don't think a good learning resource gets worse just because there's a newer alternative.

incanus77

6 minutes ago

How do you mean “these kind”?

joshuamorton

40 minutes ago

There are edge cases where this fails, but `def parse(s): return json.loads('['+re.sub('([")])\s*(["(])','\g<1>,\g<2>',re.sub('[^()\s]+','"\g<0>"',s)).replace('(','[').replace(')',']')+']')` is a surprisingly robust lisp parser.

e12e

2 hours ago

(2010)?