decode
fn
dchar decode(const scope char[] s, ref size_t idx) @safe pureDecodes and returns character starting at s[idx]. idx is advanced past the decoded character. If the character is not well formed, a UtfException is thrown and idx remains unchanged.
fn
dchar decode(const scope wchar[] s, ref size_t idx) @safe pureditto
fn
dchar decode(const scope dchar[] s, ref size_t idx) @safe pureditto