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Discussion on: Don’t pay the for-loop tax

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floridop profile image
Florido Paganelli

Three things, probably motivated by the fact that I am old:
1) readability is important, since I am old school I can't quite read this code even though I understand the functional approach (but not much the declarative)
2) The benchmark shows the problem seems to be the for implementation in JavaScript. But somebody else said the for loop is just pushed somewhere else in the libs. The point is that this is language dependent, JavaScript is what it is, there's no optimization of you use old-school coding. I mean, it's not for loops per se, it's the way these are implemented by the interpreter
3) relying on an interpreter feature like tail call "optimisation" (why would you call it like that?) It's to mess bad as relying on the C++ preprocessor that makes code ubdebuggable. But ok we're talking optimization here. Practical optimization is ugly and for a restricted group of people, let's face it.
In other words, I don't consider this nice coding.

Thanks for the article anyway, might come handy :) if you can give pointers to why the benchmarks show up like that it would be cool!

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danhomola profile image
Dan Homola Author

Thank you for your comment. To your points:

Ad 1)
I think it is only a question of getting used to it, as you say :)

Ad 2)
I'm no JavaScript engines expert, but people seem to argue, that calling a function is expensive (I'm not so sure about this argument, however I can't disprove it) and for cycles can be optimised better (for example unrolled).

Ad 3)
It does not rely on Tail Calls, my argument was merely that map & co. do not necessarily need to be implemented using cycles but for example using recursion (that would indeed need proper tail calls to avoid stack overflow).

The reason I call it optimisation is my college professor in the Runtime systems course called it that. We implemented a garbage-collected byte code language there, in my case it was a subset of Scheme, and one of the requirements (if you chose functional language) was "infinite" recursion. You can handle tail calls naïvely and overflow the stack or properly recycle the stack frames and be able to run "forever". That's why even the compat-table calls it "proper tail calls (tail call optimisation)".

The important point here is that this is an optimisation of the runtime itself, not an optimisation of the program being run.

I hope this helps to clarify things :)