Re: Is there a more elegant way to do this in D?

[Alain De Vos via Digitalmars-d-learn]

I resume in the 4 ways presented,

import std;
void main(){
        auto a=[1,0,1,1,1,0,1,0,1,1,1,0];
        
        string s = format!"%-(%s%)"(a);
        writeln(s);
        
        dchar[12] b = a.map!(to!string).joiner.array;
        writeln(b);
        
        auto conv = a.to!(ubyte[]);
        conv[]+='0';
       writeln(cast(string)conv);

        auto r = a.map!(i => cast(char)(i + '0'));
        writeln(r);
}

Why do the last two ways need "auto" as type ?