auto ref and arrays
Dan
dbdavidson at yahoo.com
Wed Nov 28 03:49:05 PST 2012
On Tuesday, 27 November 2012 at 22:09:21 UTC, Jack Applegame
wrote:
> I don't understand why auto ref doesn't work with arrays.
>
> void test1(T)(auto ref const T[] val) {}
> void test2(T)(auto ref const T val) {}
> void main() {
> int b;
> test2(b); // OK
> string a;
> test1(a); // Error: cast(const(char[]))a is not an lvalue
> }
>
> Since a is mutable itself, compiler uses ref storage class.
> cast(const(char[]))a isn't an lvalue, so it's impossible to
> pass it by ref.
>
> But cast(const int)b isn't an lvalue too. Why it's no errors in
> this case?
I thought with auto ref you dispense with the const since it
figures it out.
The below seems to work.
Thanks,
Dan
import std.traits;
import std.stdio;
void test1(T)(auto ref T val) if(!isArray!T) {
writeln("Nonarray ", typeid(typeof(val)));
}
void test1(T)(auto ref T val) if(isArray!T) {
writeln("Array ", typeid(typeof(val)));
}
void main() {
string a;
const(string) b = "string that never changes";
test1(a);
test1(b);
int[] x;
test1(x);
int y;
test1(y);
}
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