Re^2: Check multiple array elements for a single condition

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Re^3: Check multiple array elements for a single condition by afoken (Chancellor) on Aug 25, 2016 at 18:35 UTC
`if (!(@array[0]]+@array[1]))` False positive if `$array[0] == -$array[1]`. Alexander -- Today I will gladly share my knowledge and experience, for there are no sweeter words than "I told you so". ;-)	[reply] [d/l] [select]
Re^4: Check multiple array elements for a single condition by Linicks (Scribe) on Aug 25, 2016 at 18:40 UTC
Please explain what you mean by 'false positive'? Thanks, Nick	[reply]
Re^5: Check multiple array elements for a single condition by afoken (Chancellor) on Aug 25, 2016 at 18:47 UTC
Please explain what you mean by 'false positive'? `#!/usr/bin/perl use strict; use warnings; sub are_both_zero { my @array=@_; print "In the array (",join(', ',@array),"), "; if (!($array[0]+$array[1])) { print "both elements are zero.\n"; } else { print "at least one element is not zero.\n"; } } are_both_zero(3,-5); are_both_zero(3,0); are_both_zero(0,-5); are_both_zero(0,0); are_both_zero(3,-3);` [download] Output: `In the array (3, -5), at least one element is not zero. In the array (3, 0), at least one element is not zero. In the array (0, -5), at least one element is not zero. In the array (0, 0), both elements are zero. In the array (3, -3), both elements are zero.` [download] See also https://en.wikipedia.org/wiki/False_positive. Alexander -- Today I will gladly share my knowledge and experience, for there are no sweeter words than "I told you so". ;-)	[reply] [d/l] [select]
Re^6: Check multiple array elements for a single condition by Linicks (Scribe) on Aug 25, 2016 at 18:58 UTC
Re^3: Check multiple array elements for a single condition by RonW (Parson) on Aug 26, 2016 at 19:37 UTC
Try `if (!(@array[0] \| @array[1]))` instead. (For reasons afoken stated.)	[reply] [d/l]
Re^4: Check multiple array elements for a single condition by afoken (Chancellor) on Aug 27, 2016 at 10:05 UTC
Try `if (!(@array[0] \| @array[1]))` instead Don't, for the reason Marshall++ explained. Micro-optimising code to avoid typing a few characters does not improve performance, and makes maintenance a nightmare (if overused). Also, your code assumes integers, right? I would have to look up the binary representation(s) of a float 0.0 to see if all bits are 0 there. If not, this probably won't work, resulting once again in wrong results (false negatives, in this case). Maybe floats depend on the CPU and / or math emulation library used, so the result would also depend on the machine it is running on. No, thanks. I prefer code that does not make me think about such issues. For two or three elements, explicitly compare the elements. For more, see my generalised posting. Playing golf is a completely different story, but then, the array's name would not be five letters long. Alexander -- Today I will gladly share my knowledge and experience, for there are no sweeter words than "I told you so". ;-)	[reply] [d/l]