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• Pad-trim

Rpadstr

Pad a string with spaces on the right.

(rpadstr x len) extends the string x to length len by adding spaces on the right. For instance,

(rpadchars "foo" 5)
   -->
"foo  "

This is completely dumb: we don't try to account for newlines, tabs, or anything like that, and just add #\Space characters until reaching the desired width.

If no new spaces are needed, x is returned unchanged and no consing or coercion is performed.

Definitions and Theorems

Function: rpadstr

(defun rpadstr (x len)
  (declare (xargs :guard (and (stringp x) (natp len)))
           (type string x)
           (type integer len))
  (mbe :logic
       (implode (rpadchars (explode x) len))
       :exec
       (let* ((x-len (length (the string x)))
              (diff (- len x-len)))
         (if (> diff 0)
             (let ((spaces (repeat diff #\Space)))
               (implode (mbe :logic (append-chars x spaces)
                             :exec
                             (if (zp x-len)
                                 spaces
                               (append-chars-aux x (- x-len 1)
                                                 spaces)))))
           x))))

Theorem: stringp-of-rpadstr

(defthm stringp-of-rpadstr
  (stringp (rpadstr x len))
  :rule-classes :type-prescription)

Theorem: len-of-explode-of-rpadstr

(defthm len-of-explode-of-rpadstr
  (implies (force (stringp x))
           (equal (len (explode (rpadstr x len)))
                  (max (length x) (nfix len)))))

Theorem: streqv-implies-equal-rpadstr-1

(defthm streqv-implies-equal-rpadstr-1
  (implies (streqv x x-equiv)
           (equal (rpadstr x len)
                  (rpadstr x-equiv len)))
  :rule-classes (:congruence))

Theorem: istreqv-implies-istreqv-rpadstr-1

(defthm istreqv-implies-istreqv-rpadstr-1
  (implies (istreqv x x-equiv)
           (istreqv (rpadstr x len)
                    (rpadstr x-equiv len)))
  :rule-classes (:congruence))