Simple overloading without complications

[Adam Sansier via Digitalmars-d-learn]

On Tuesday, 12 July 2016 at 18:52:08 UTC, Meta wrote:
> On Tuesday, 12 July 2016 at 04:23:07 UTC, Adam Sansier wrote:
>> Now, I could simply make Do a template method but then this 
>> prevents it being a virtual function.
>>
>> void Do(T)(T name) if (is(T == string) || is(T == int))
>> {
>>     Init_Data();
>>
>>     static if (is(T == string))
>>     {
>>         ...Get index from name
>>     }
>>
>>     ....
>> }
>
> You could always use std.variant.algebraic which implements 
> runtime polymorphism:
>
> import std.algebraic;
>
> alias intOrString = Algebraic!(int, string);
>
> void Do(intOrString indexOrName)
> {
>     Init_Data();
>
>     int index = indexOrName.visit!(
>         (int i) => i,
>         (string s) => getIndexByName(s),
>     );
>
>     ....
> }

I thought about this, but kinda hacky. Because I'm using wstring 
I would basically have to do:

> alias intOrString = Algebraic!(int, string, wstring);
>
> void Do(intOrString indexOrName)
> {
>     Init_Data();
>
>     int index = indexOrName.visit!(
>         (int i) => i,
>         (string s) => getIndexByName(to!wstring(s)),
>         (wstring s) => getIndexByName(s),
>     );
>
>     ....
> }

It's not terrible, but not better than using templates, which 
would be more performant.

void Do(T arg) if (is(arg == string) || is(arg == int) || is(arg 
== wstring)
{
    int i = 0;
    Init_Data();
    static if (is(arg == string) || is(arg == wstring))
    {
        wstring s;
        static if (is(arg == string))
            s = to!wstring(arg);
        else
            s = arg;
        // Find i for string
        i = Findi(arg);
    } else
        i = arg;
    ....
}


It's not very elegant either but basically works and solves the 
problem... and also does it in one function. It's probably as 
close as one can get in D to what I want, I'm hoping someone find 
a better way.