On Sun, 01 Aug 2010 19:22:42 -0400, bearophile <[email protected]>
wrote:
Time ago an automatic tool has said that in a line of C code similar to:
int r = x / y * z;
a division operator followed by a mult is confusing, and to add
parentheses to improve the code:
int r = (x / y) * z;
When values are integral the position of parentheses can change the
value of the expression:
void main() {
int x = 10;
int y = 3;
int z = 5;
assert(x / y * z == 15);
assert((x / y) * z == 15);
assert(x / (y * z) == 0);
}
That has nothing to do with integral arguments. That has to do with
precedence.
assert(x / y * z == (x / y) * z);
is going to pass no matter what the value/type of x, y, z.
And given the values you have for x y z, the following statement is also
true regardless of type:
assert(x / y * z != x / (y * z));
Turning 'x / y * z' into a D syntax error (as done in bug
http://d.puremagic.com/issues/show_bug.cgi?id=4077 ) looks excessive to
me. A warning seems enough, but Walter is not a lover of warnings (and
sometimes I agree, I'd like to turn three D warnings into errors). What
do you think?
No warning, no error. It's natural to assume that operations are
performed from left to right. I don't find it confusing at all.
-Steve
