Re: Changing Template Static Ifs to Recursion

[jmh530 via Digitalmars-d-learn]

On Wednesday, 31 May 2017 at 19:22:18 UTC, Stefan Koch wrote:

You could also use string mixins.
Which will be more efficient then recursion.

I try to avoid string mixins unless I can't help it. 
Nevertheless, I made an effort to try to get it to work and below 
seems to be working. I still have to use some recursion to 
generate the string.

The downside is that this version can't be @nogc, correct?


auto ref opIndex(Slices...)(Slices slices)
        if (Slices.length == Types.length)
{
        template GetParensi(size_t i)
        {
                const char[] GetParensi = "this.underlying[" ~ i.stringof ~
                                                                                
"][slices[" ~ i.stringof ~ "]]";
        }

        template GenParens(T...)
        {
                static if (T.length > 0)
                {
                        static if (T.length == 1)
                                const char[] GenParens = GetParensi!(T.length - 
1);
                        else static if (T.length > 1)
                                const char[] GenParens = GenParens!(T[0 .. $ - 1]) ~ 
", " ~
                                                                                
                GetParensi!(T.length - 1);
                }
        }
        
        const char[] GenResult = "foo!(Names)(" ~ GenParens!Slices ~ ")";
        
        return mixin(GenResult);
}