On 12/16/19 9:38 AM, Per Nordlöw wrote:
What is the fastest way to check whether a class reference is an
instance of a
bottom equal to any in a set of classes? My current try is something like
class C {}
class X : C {}
class Y : C {}
class Z : C {}
....
bool pred(scope const Object object)
{
return (cast(const(X))object ||
cast(const(Y))object ||
cast(const(Z))object ||
...);
}
or is it better to switch on the non-scoped (via some existing
string-to-string
function `unscoped`) part of the `typeid(object).name` like
bool pred(scope const Object object)
{
const name = typeid(object).name.unscope;
import std.algorithm.comparison : among;
return name.among!(X.stringof,
Y.stringof,
Z.stringof,
...);
}
?
I'd compare the typeid directly:
auto tid = typeid(object);
return(tid is typeid(X) || tid is typeid(Y) || tid is typeid(Z) || ...)
If you are doing a cast(const(X))object, what you are doing is each time
traversing the linked-list of typeids anyway doing the same as the
above, but doing extra work. So this should be faster.
-Steve
