Bill Clementson's Blog: JavaScript and Lisp | Hacker News Reader

Bill Clementson's Blog: JavaScript and Lisp

bc.tech.coop

31 pointsr11t12 comments

Using JavaScript 1.8 expression closures:

  function Y(X)
      (function(procedure)
          X(function(arg) procedure(procedure)(arg)))
              (function(procedure)
                  X(function(arg) procedure(procedure)(arg)))

Nice but, anonymous recursion is possible with arguments.callee.

More on arguments.callee:

https://developer.mozilla.org/En/Core_JavaScript_1.5_Referen...

arguments.callee is deprecated in javascript 1.4. Use function name instead, so interpreter will have chance to perform tail recursion. Give names to your anonymous functions anyway: it will be much easier to trace them.

Example of anonymous recursive function with arguments.callee:

  var factorial=function(n) {
     return (!(n>1))? 1 : arguments.callee(n-1)*n;
  }

Example of anonymous recursive function without arguments.callee:

  var factorial=function factorial(n) {
     return (!(n>1))? 1 : factorial(n-1)*n;
 }

Tried Doug Crockford's little Javascripter: (define loop (lambda (x) (loop x))) (loop 1)

Result in Firefox: "Too much recursion"

I'm still surprised I didn't flunk B521 when Dan Friedman put something like this in my Java implementation of a Scheme interpreter and it blew up after some finite number of iterations.

It might have worked if method calls were properly tail-recursive!

Helped me find a cool video from this Waldemar Horwat guy. http://www.youtube.com/watch?v=Kq4FpMe6cRs

> will recognize that functions in JScript are fundamentally the Lambda Calculus

i would have thought you could say that about functions in any language...

Except languages where you can't pass functions as arguments or return them as results.

Horror! I didn't know such atrocities existed shudder ;)

you're right. i should have said "first class functions" (which narrows the field somewhat).

JavaScript is implementation of Scheme (dialect of Lisp) with Java-like syntax.

Or as I like to say "JavaScript is Scheme in C drag".

Reply on news.ycombinator.com