Re: std.meta.Replace using index

[Ali Çehreli via Digitalmars-d-learn]

On 07/28/2017 12:04 PM, Ali Çehreli wrote:
On 07/28/2017 01:22 AM, Nicholas Wilson wrote:
Hi
I want to replace each occurrence of a particular type in an AliasSeq
with a type from another AliasSeq (the both have the same length) with
the corresponding index

i.e. (int long long float) (byte char double dchar)  replacing long
should yield (int char double float) std.meta.Replace would see to do
the trick except the lambda depends in the index and I'm not sure how to
pass that.


I think it works:

template replace(T) {
    template inside(Src...) {
        template from(Dst...) {
            import std.meta;
            enum f = staticIndexOf!(T, Src);
            static if (f == -1) {
                alias from = Src;
            } else {
                alias from = AliasSeq!(Src[0 .. f], Dst[f], 
inside!(Src[f + 1 .. $]).from!(Dst[f + 1 .. $]));
            }
        }
    }
}

unittest {
    import std.meta : AliasSeq;
    replace!long
        .inside!(long, int, long, long, float, long)
        .from!(int, byte, char, double, dchar, real) a;
    static assert(is (typeof(a) == AliasSeq!(int, int, char, double, 
float, real)));
}

void main() {
}

Ali