Stewart Gordon wrote:
Jason House wrote:
<snip>
Method 1:
if (x !in y)
foo();
else{
auto z = x in y;
bar(z);
}
Method 2:
auto z = x in y;
if (z is null)
foo;
else
bar(z);
Method 1 essentially calls in twice while method 2 calls in once.
<snip>
But there's no requirement to look it up after finding out whether it's
there or not.
And how's it any different from
if (x in y) {
auto z = x in y;
bar(z);
} else {
foo();
}
or even
if (x in y) {
bar(y[x]);
} else {
foo();
}
?
Besides, why would any decent compiler not optimise it to a single lookup?
Interesting fact: LDC currently optimizes the first case (at -O3), but not the
second. That's because it apparently uses a different libcall for 'x in y' than
it does for 'y[x]' -- even though the code in the libcalls are equivalent.
I think I just found inspiration for my next commit :).
