bearophile wrote:
simendsjo:
I haven't worked much with AA's, but I find the "key in aa returns a
reference to the value" to be handy. I think it's better than the following:
int value;
if( 1 in a )
value = a[1];
or a[1] in a try/catch or other implementations.
Your examples have shown me that probably the current design can't be made
safe, and you can't use in SafeD code.
But performing "x in AA" is a very useful operation that I want to perform in
SafeD code.
And in my opinion this code:
int value;
auto ptr = 1 in a;
if (ptr)
value = *ptr;
Doesn't look better than:
int value;
if (1 in a)
value = a[1];
2) I don't know what you mean. Does a single lookup often involve
several under the hood?
If your compiler is naive then code like this:
if (1 in a)
value = a[1];
requires to perform two searches inside the hash, the first to tell if the key
is present, and the second to find it again and fetch its value.
A bit better compiler (LDC is already able to do this) can recognize that you
are performing two nearby key searches with the same key, and it can remove the
second one, essentially replacing that code with this one:
int value;
auto ptr = 1 in a;
if (ptr)
value = *ptr;
Bye,
bearophile
You can always use:
auto value = 1 in a;
if (value) // needs != null? Haven't looked at this in the spec yet.
//work with *value
But if the compiler can optimize the calls either way, and this is
unsafe, a safer way sounds nice.
