String-Read-Byte!

(string-read-byte! string) -> integer or #f

Destructively reads a single byte from the given string. If the string is empty, #f is returned.

Examples:

>> (define a "abcdefghijklmnopqrstuvwxyz")
:: "abcdefghijklmnopqrstuvwxyz"
>> (string-read-byte! a)
:: 97