Comparison Style
llanitedave
llanitedave at veawb.coop
Thu Apr 25 10:19:04 EDT 2013
On Wednesday, April 24, 2013 10:57:49 PM UTC-7, Chris Angelico wrote:
> On Thu, Apr 25, 2013 at 3:49 PM, llanitedave <llanitedave at veawb.coop> wrote:
>
> > Given that
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> >
>
> > s = some static value
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> > i = a value incremented during a loop
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> >
>
> > I'm used to comparing them as
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> >
>
> > if i == s:
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> > # some code
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> >
>
> > But for some unknown reason I did a switch
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> >
>
> > if s == i:
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> > # same code
>
> >
>
> > It didn't seem to make any difference at first glance, so I just got to wondering --
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>
>
> It won't make any difference in any sort of sane code. If there's any
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> situation in which == is not reflexive, something seriously nasty is
>
> going on.
>
>
>
> > Is there a standard for comparison order? Is there any kind of performance difference? Is there even a tradition for one or the other? Are there any gotchas?
>
>
>
> It's conventional to compare variables to constants, not constants to
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> variables (even in C where there's the possibility of mucking up the
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> operator, most people still compare variables to constants). I'd
>
> normally use "i == s" there, treating s as a constant for the purpose
>
> of the loop. Unless you're deliberately being poetical, language such
>
> as "Three is the number thou shalt count" is distinctly abnormal, so
>
> saying "if (5 == i)" is equally awkward. It's nothing major; mostly
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> it's like the algebraic convention of putting the more-known elements
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> earlier in a term (eg 2πix - 2 is known, 3.14159.... is mostly known,
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> i is imaginary but at least it's constant, and x is unknown).
>
>
Thanks, Chris. That's kind of along the lines of what I was thinking. Visually, the code just looked wrong, and I figure if for no other reasons than readability it's preferable in the traditional way.
It's nice to know, though, that the next time dyslexia strikes it's not necessarily a horrible thing.
>
> > Do I need to get a hobby?
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>
>
> I thought programming WAS a hobby?
>
I meant a safer, easier, and more mainstream hobby, like base jumping or motorcycle aerobatics or something.
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