Author: Dann Corbit
Date: 17:03:27 09/20/01
Go up one level in this thread
On September 20, 2001 at 18:24:07, Antonio Dieguez wrote:
>can you tell me?
Depends on a zillion things. Sometimes, you cannot make that translation.
For instance, if you want to substitute & for &&, then you must have both
operands be boolean (IOW: _ONLY_ take on the values 0 and/or 1).
This is not a valid translation:
int a = 1;
int b = 2;
if ((a && b) == (a & b) puts("My compiler is broken);
If the cost of evaluating the operands is very high, then it may be better to
use &&.
Example:
if (foo() && bar()) then foobar();
Suppose that foo() is fast, and bar() is really slow. Further, foo() is 0 most
of the time. Then you would rather have the short circuit evaluation and
branch.
Missed branch predictions are expensive on newer chips, but it is not always an
easy thing to see when one method is faster than the other.
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