True when Code represents the character at the 1-based Index
position in String. If Index is unbound the string
is scanned from index 1. Raises a domain error if Index is
negative. Fails silently if Index is zero or greater than the
String. The mode string_code(-,+,+) is
deterministic if the searched-for Code appears only once in String.
Tag confusing pages with doc-needs-help|Tags are associated to your profile if you are logged in