On 06/21/2016 06:09 PM, KatolaZ wrote:
On Tue, Jun 21, 2016 at 05:47:59PM +0900, Simon Walter wrote:
[cut]
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.
I didn't say that short-circuiting is a peculiarity of C :)
Aha! You certainly didn't. I was surprised that "non-short-circuiting"
logical operators even existed.
I simply
said that short-circuiting is how C evaluates conditional
expressions. There are many cases (such as that of FORTRAN) in which
short-circuiting can be enabled or disabled at compile time, many
other cases (e.g. most of the dialects of BASIC and some other
esoteric languages) in which short-circuting does not exist, and many
more cases in which the language supports both eager and short-circuit
boolean operators (e.g., Java, Python, Perl, Ruby, etc.)
Boolean expressions in C are always subject to short-circuting.
Interesting. And here I was taking "short-circuiting" for granted. Well,
you learn something new everyday. I will be sure to keep that in mind.
Can you to point me to those other operators that do not "short-circuit"
in Java, Python, Perl, and Ruby? Are the operators different, or do you
have to change the behaviour with a switch?
I am thinking we might use single ampersand or pipe (bitwise). Can we
use bitwise operators as what would be a non-short-circuiting logical
operator in C (or other languages)?
Very interesting!
Simon
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