The following:
import std.stdio : writefln;
import std.range.primitives : isInputRange, hasLength;
void main() {
size_t[] a = [1, 2, 3, 4, 5, 6, 7, 8, 9];
doSomething(a); // works
doSomething(a[0..5]);
// ---> Error: template slices.doSomething cannot deduce function
from argument types !()(ulong[]), candidates are:
// slices.d(11): slices.doSomething(R)(ref R r) if
(isInputRange!R && hasLength!R)
doSomething!(size_t[])(a[0..5]);
// ---> Error: doSomething (ref ulong[] r) is not callable
using argument types (ulong[])
}
void doSomething(R)(ref R r)
if (isInputRange!R && hasLength!R) // etc..
{
foreach (ref n; r) {
writefln("%d * 2 = %d", n, n * 2);
}
}
//EOF
a[0..5] is not recognized as size_t[]. If I give the compiler a
hint with !(size_t[]), it complains again, i.e. I can not pass
the slice as a reference.
A workaround is
size_t[] b = a[0..5];
doSomething(b);
However, this comes with a serious performance penalty in for
loops (even if I predefine b and reuse it in the loop).
to!(size_t[])(a[0..5]) is even worse.
Any thoughts or tips?
