Maximum call stack size exceeded while evaluating lazy sequence

[hallettj]

This is probably an issue for the upstream ClojureScript project. But I wanted to post this to see if anyone knows of a workaround.

I am working on a blog post on Mori with some examples of lazy evaluation. Here is what I have at the moment:

// With no arguments, `range` returns a lazy sequence of all whole
// numbers from zero up.
var non_neg_ints = mori.range();

// Dropping the first element, zero, results in a sequence of all of
// the natural numbers.
var nats = mori.drop(1, non_neg_ints);

// Let's take just the powers of 2.
var ln_2   = function(n) { return Math.log(n) / Math.LN2; };
var pows_2 = mori.filter(function(n) { return ln_2(n) % 1 === 0; }, nats);

// What are the first 10 powers of 2?
console.log(
    mori.take(10, pows_2)
);

// Outputs:
// > (1 2 4 8 16 32 64 128 256 512)

That works nicely. But if I change the number of evaluated sequence elements from 10 to 15 (in the node repl) I get a stack overflow exception:

> mori.take(15, pows_2);

/home/jesse/tmp/node_modules/mori/mori.js:26
b?this.Ca===b.Ca:l};Ub.prototype.toString=m("Ca");function D(a){if(a==j)return
                                                                    ^
RangeError: Maximum call stack size exceeded

[hallettj]

Ok, I confirmed that this is an upstream bug:

cljs.user> (defn nats [] (drop 1 (range)))
cljs.user> (defn log-2 [n] (/ (Math.log n) Math.LN2))
cljs.user> (defn is-pow-2 [n] (= (mod (ln-2 n) 1) 0))
cljs.user> (defn pows-2 [] (filter is-pow-2 (nats)))
cljs.user> (take 10 (pows-2))
(1 2 4 8 16 32 64 128 256 512)
cljs.user> (take 15 (pows-2))
Compilation error: RangeError: Maximum call stack size exceeded

[swannodette]

Yes recently fixed this one in ClojureScript will cut a new release of Mori soon to address.

[hallettj]

Nice! Thanks for the quick response! And by the way, I am really enjoying this library.

[swannodette]

Fixed, 0.2.4 just went out.

[hallettj]

Very nice! Thanks again!

[hallettj]

By the way, I published that post: http://sitr.us/2013/11/04/functional-data-structures.html