On 06/21/2016 05:28 PM, KatolaZ wrote:
On Tue, Jun 21, 2016 at 08:22:41AM +0200, Edward Bartolo wrote:
[cut]
I studied 'and' and 'or' boolean operators back when I studied Delphi
Pascal. I am embarrassed to have written such a stupid thing. It must
be due to the fact I wrote the email just before going to bed.
AND: requires ALL sub-expressions to be true to evaluate to true
i.e. Q = A ^ B ^ C ^ .... D
Q = 1 if and only if A = B = C = .... D = 1
OR: only requires ONE sub-exression to be true to evaluate to true
i.e. Q = A v B v C v .... D
Q = 1 if any Ai = 1
These properties are used by compilers to optimize on boolean
expression evaluation. If I remember well, there are also specific
Be careful, because conditional expressions in C are subject to
"short-circuiting", meaning that only the minimum number of
expressions sufficient to determine the value of a chain of && and ||
will be evaluated. In particular, a chain of || expressions will be
evaluated until there is one that evaluates to TRUE (!=0), while a
chain of && is evaluated until there is one of them which evaluates to
false (==0).
Isn't that how AND and OR work in most programming languages? Mind you,
I am not familiar with that many.
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