iteration over a string

[Diggory]

Most algorithms for strings need the offset rather than the 
character index, so:

foreach (i; dchar c; str)

Gives the offset into the string for "i"

If you really need the character index just count it:

int charIndex = 0;
foreach (dchar c; str) {
    // ...

    ++charIndex;
}

If strings were treated specially so that they looked like arrays 
of dchars but used UTF-8 internally it would hide all sorts of 
performance costs. Random access into a UTF-8 string by the 
character index is O(n) whereas index by the offset is O(1).

If you are using random access by character index heavily you 
should therefore convert to a dstring first and then you can get 
the O(1) random access time.