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conditional statement with ||

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Leor Greenberger on 28 Sep 2011
Say I have
If A && B && C
...do something if A = B = C = true
end
Is it faster, however to do:
If ~(A || B || C)
..do something if A or B or C = false
end
I am wondering if the latter statement is faster because it should be able break if any of the conditions are false and not test the rest. But I am wondering if the negation forces all of the conditions to be tested first?
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Accepted Answer

Fangjun Jiang on 28 Sep 2011
If A is false, then A && B will be short-circuited. No need to use the latter approach. Use the first one because it's easy to read.
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More Answers (1)

Walter Roberson on 28 Sep 2011
The two expressions are not equivalent.
A && B && C
is true only if A and B and C are all true.
~(A||B||C)
is true only if A and B and C are all false, not if one of them is false.
The logical or equivalent of A && B && C is
~(~A || ~B || ~C)
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Fangjun Jiang on 29 Sep 2011
+1, that's another sharp catch!

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