After a recent discussion on this list about tail-const class
references, it became rather clear that someone interested would have
to implement the thing if we were to have it. So I did it. See
enhancement request 5325 for an explanation and a patch.
<http://d.puremagic.com/issues/show_bug.cgi?id=5325>
Let's hope Walter likes my patch.
In the tail-const thread, I proposed the challenge of making this code
work when an array of const object is passed as an argument:
T[] giveMeASortedArray(alias Predicate, T)(T[] t) {
// creating new array of the same length but with assignable
elements
auto copy = new Unqual!(typeof(t[0]))[t.length];
foreach (index, value; t)
copy[index] = value;
// sorting the copy
sort!(Predicate)(copy);
return copy;
}
Well, with the patch I made it now works!... irrespective of the type
attribute (const,immutable,shared,inout). The only modification
required to Phobos is to make to!string() compile when passed a
const(Object) because somehow 'sort' requires that.
Here is how the function is invoked:
void main() {
int*[] a = giveMeASortedArray!("a < b")(new int*[12]);
Object[] b = giveMeASortedArray!("a < b")(new Object[12]);
const(int*)[] c = giveMeASortedArray!("a < b")(new
const(int*)[12]);
const(Object)[] d = giveMeASortedArray!("cast(void*)a <
cast(void*)b")(new const(Object)[12]);
}
See the strange predicate for the const(Object) version? That's because
opCmp() in Object doesn't work with const.
Two minor modifications are required in Phobos to make the above
compile. First, to!string(const(Object)) needs an implementation
because somehow 'sort' requires it. Also template std.traits.isMutable
needed an adjustment so that swap()'s template constrains are satisfied.
--
Michel Fortin
michel.for...@michelf.com
http://michelf.com/
