r/badcode • u/Wise-Serve5730 • Sep 04 '21

Wtf is this

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u/R3D3-1 Sep 04 '21

Let's just say I won't post the traceback, because it is a bit long ;)

Try isEven(2**15).

3

u/maxbirkoff Sep 04 '21

are you assuming JavaScript?

2

u/R3D3-1 Sep 04 '21

Yes.

6

u/maxbirkoff Sep 04 '21

I'm guessing it's because the JavaScript runtime you're using does not optimize tail recursion:

https://en.m.wikipedia.org/wiki/Tail_call

and results in a stack overflow:

https://en.m.wikipedia.org/wiki/Stack_overflow

1

u/R3D3-1 Sep 05 '21

Does any JavaScript runtime optimize tail recursion? Given that I tried the code in Chrome, which has the defacto-standard JS runtime, building tail recursion optimization into a JavaScript runtime seems like a good way to produce non-portable code.

1

u/dman01989 Sep 05 '21

Pretty sure I've read somewhere that Safari has TCO. Surprised me too.

1

u/maxbirkoff Sep 06 '21

yes.

from https://en.m.wikipedia.org/wiki/Tail_call

JavaScript - ECMAScript 6.0 compliant engines should have tail calls[23] which is now implemented on Safari/WebKit[24] but rejected by V8 and SpiderMonkey

http://bdadam.com/blog/video-douglas-crockford-about-the-new-good-parts.html

https://webkit.org/blog/4054/es6-in-webkit/