# [racket] How fast is zero? was: Find nth term of a List

 From: Robby Findler (robby at eecs.northwestern.edu) Date: Thu Sep 27 12:19:26 EDT 2012 Previous message: [racket] How fast is zero? was: Find nth term of a List Next message: [racket] How fast is zero? was: Find nth term of a List Messages sorted by: [date] [thread] [subject] [author]

```If you have a loop where the exit condition test is a significant
contribution to the time, then we should look at the loop to answer
these questions, as it will depend on what else you're doing there.
(This seems like a rare situation to me, but not entirely out of the
realm of possibility).

Otherwise, I'd ignore the speed issue.

Robby

On Thu, Sep 27, 2012 at 11:10 AM, Tim Brown <tim.brown at cityc.co.uk> wrote:
> What is the difference in correctness between "(= x 0)" vs. "(zero? x)"?
>
> Fast is relevant to some questions (solutions) I have -- terminating tight
> loops etc. And given a choice of (eq? 0 x), (= 0 x) and (zero? x), which
> would, and which should take the shortest time to perform 10^12 times?
>
> Maybe I'm thinking a bit too much like a C programmer -- (!x)... works for
> me as a test in so many ways; that I tend to want to use something like it
> when I'm writing in other languages. (Where I should be using zero? false?
> and/or null?).
>
> Tim
>
> On 27/09/12 16:50, Matthias Felleisen wrote:
>>
>> Fast is so irrelevant for this question.
>>
>> Correct is what really matters.
>>
>>
>>
>> On Sep 27, 2012, at 11:45 AM, Tim Brown wrote:
>>
>>> On 26/09/12 15:31, Marco Morazan wrote:
>>>>
>>>> 1. Is eq? the most natural way to test the equality of numbers? (minor
>>>> quibble)
>>>
>>>
>>> I was wondering this, myself, earlier, but is zero? the fastest way to
>>> test for zero-ness?
>>>
>>> Tim
>
>
> --
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```

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