On Wed, Aug 02, 2017 at 11:06:03AM -0700, H. S. Teoh via Digitalmars-d-learn
wrote:
[...]
> auto byPair(AA)(inout(AA) aa)
> {
> alias Modifiers = std.traits.getModifiers!AA;
> struct Result {
> std.traits.ApplyModifiers!(Slot*, Modifiers) slot;
> ... // range methods here
> }
> return Result(aa);
> }
>
> Of course, getModifiers and ApplyModifiers are fictitious Phobos
> templates, but you get the idea.
[...]
Hmm, actually, they don't have to be fictitious; here's an actual,
compilable example:
struct Slot {
Slot* next;
string key;
int value;
}
struct AA {
Slot*[] slots;
}
auto byPair(AA)(AA aa)
{
import std.traits : QualifierOf;
alias Qual = QualifierOf!AA;
struct Result {
Qual!(Slot)* slot;
bool empty() { return slot is null; }
auto front() {
struct Front {
Qual!string key;
Qual!int value;
}
return Front(slot.key, slot.value);
}
void popFront() {
slot = slot.next;
}
}
return Result(aa.slots[0]);
}
unittest {
AA aa;
const(AA) constAa;
immutable(AA) immAa;
auto mutPair = aa.byPair;
static assert(is(typeof(mutPair.front.value) == int));
auto constPair = constAa.byPair;
static assert(is(typeof(constPair.front.value) == const(int)));
auto immPair = immAa.byPair;
static assert(is(typeof(immPair.front.value) ==
immutable(int)));
}
T
--
If Java had true garbage collection, most programs would delete themselves upon
execution. -- Robert Sewell
