Re: Finding the max()/min()


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Re: Finding the max()/min()

by benizi (Hermit)

on Nov 12, 2004 at 21:58 UTC ( [id://407540]=note: print w/replies, xml )

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in reply to Re: Finding the max()/min()
in thread Finding the max()/min()

Very cool. <nitpick>...but there's still a comparison; it's just hidden in the abs() function: (roughly:) abs(x) := x >= 0 ? x : -x.</nitpick>

[OT] Reminds me of a programming assignment where we were supposed to put the square roots of the integers from 1-100 inclusive into two groups with roughly equal sums. I used the fact that sqrt(x) + sqrt(x+3) is very close to sqrt(x+1) + sqrt(x+2) and managed to outperform all the other submissions by several orders of magnitude in both speed and "difference in sum". (Yea math!)

Comment on Re: Finding the max()/min()

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Re^2: Finding the max()/min() by etcshadow (Priest) on Nov 12, 2004 at 22:12 UTC
The nitpick is perfectly valid... I almost made a note of it. Of course, it would be possible (though silly) to implement an abs function without a comparison, such as `sub abs { sqrt($_[0]**2) }`. There's probably some mathematical identity for the abs of the difference of two numbers... but I didn't get enough sleep last night to think about what it might be :-) `------------ :Wq Not an editor command: Wq` [download]	[reply] [d/l] [select]
Re^2: Finding the max()/min() by Anonymous Monk on Dec 12, 2023 at 22:18 UTC
abs(x) can be implemented mathematically as sqrt(x**2). Or it can be implemented at the memory management level by just dropping the bit that carries the negative sign. So it's not necessarily a hidden comparison.	[reply]

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