A Lisp interpreter in TypeScript | Hacker News Reader

A Lisp interpreter in TypeScript

oki-osk.jp

58 pointssuzuki13 comments

The Lisp in 1,200 lines of Dart, which has macros, quasi-quotation and tail-call optimization (https://news.ycombinator.com/item?id=9903332), was translated into 1,390 lines of TypeScript. It runs on browsers.

If you are interested in the future of Lisp in the context of browsers or Nodejs, take a look at this: http://lispblog.xach.com/post/138667931963/lisp-and-webassem...

Why does the foldl function use a while loop?

I think it's just manual tail-call optimization?

Why not? map, fold/reduce are not necessarily implemented as the textbook says.

Certainly not. The foldl is a part of the TypeScript program that implements the Lisp.

By the way, as for "while" in the implemented Lisp, it is defined with recursion and will be executed with tail-call optimization. See

  (defmacro while (test &rest body)
    (let ((loop (gensym)))
      `(letrec ((,loop (lambda () (cond (,test ,@body (,loop))))))
         (,loop))))

in the const prelude of lisp.ts (http://www.oki-osk.jp/esc/typescript/lisp/lisp.ts.html).

Thanks for this information.

My point was more that map and reduce do not inherently require a recursive implementation and can be implemented directly as loops.

I don't follow closely TypeScript: is tail-call merging done when compiling to Javascript or is the Javascript runtime responsible for this behavior?

No, neither. That behavior is implemented in the same way as in the Lisp in Dart (http://www.oki-osk.jp/esc/dart/lisp-en.html#4).

I will now write all my comment in Kanjis. It's too beautiful.

Thus, yet again, sort-of-validating Greenspun's 10th Rule.

I'm not complaining... just observing :).

As much as I love a good Greenspun invocation, I don't think this really counts:

> Any sufficiently complicated C or Fortran program contains an ad hoc, informally-specified, bug-ridden, slow implementation of half of Common Lisp.

isn't about the inevitability of literally implementing a Lisp interpreter.

It's about something more abstract. see: http://c2.com/cgi-bin/wiki?LevelsOfGreenspunning

Mostly agreed. Which is why I said "sort-of-validating".

... so that I would be technically correct. Which, as we all know, is the best kind of correct. (Source: Futurama)

It's still got a good shot at validating Zawinski's Law of Software Envelopment.

> Every program attempts to expand until it can read mail. Those programs which cannot so expand are replaced by ones which can.

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