To either a `foreach(dchar c; str)` or `for ( ; !str.empty ; std.popFront() ) auto c = str.front;`. The sad truth is that manually looping while explicitly doing `std.utf.decode` is faster than anything simple that is built in. Like quite a lot faster. I usually don't bother too much with this detail (as I hope it will just solve itself long-term), I think some functions (like `find`) warrant the extra code for extra speed.