Calculate the keyspace of a password.

keyspace.lisp

(defun keyspace (string)
  "Calculates the keyspace of an ASCII string; this can be used to
deny certain passwords from being used."
  ;; Hopefully the implementation is a smart string and knows how long
  ;; it is automatically.
  (let ((length (length string))
        (capabilities (make-hash-table :test #'eq)))

    ;; O(n)
    (loop for ele across string
          do
             (cond
               ((upper-case-p ele)
                (setf (gethash :upper-case capabilities) 26))
               ((lower-case-p ele)
                (setf (gethash :lower-case capabilities) 26))
               ((digit-char-p ele)
                (setf (gethash :digit capabilities) 10))
               (t
                (setf (gethash :other capabilities) 33))))

    ;; O(n)
    (expt (loop for value being the hash-values of capabilities
           sum value)
          length)))