- string-anyprocedure
Checks to see if every/any character in s satisfies pred proceeding from left (index start) to right (index end).
The predicate is "witness-generating":
- If string-any returns true, the returned true value is the one produced by the application of the predicate.
- If string-every returns true, the returned true value is the one produced by the final application of the predicate to s[end-1].
If string-every is applied to an empty sequence of characters, it simply returns #t.
The names of these procedures do not end with a question mark--this is to indicate that they do not return a simple boolean (#t or #f), but a general value.