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Pad-trim

Rpadchars

Pad a character-list with spaces on the right.

(rpadchars x len) extends the character list x to length len by adding spaces on the right. For instance,

(rpadchars '(#\f #\o #\o) 5)
   -->
'(#\f #\o #\o #\Space #\Space)

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 is performed.

Definitions and Theorems

Function: rpadchars

(defun rpadchars (x len)
  (declare (xargs :guard (and (character-listp x) (natp len)))
           (type integer len))
  (mbe :logic
       (append (make-character-list x)
               (repeat (nfix (- (nfix len) (len x)))
                       #\Space))
       :exec
       (let* ((x-len (length (the list x)))
              (diff (- len x-len)))
         (if (> diff 0)
             (append x (repeat diff #\Space))
           x))))

Theorem: character-listp-of-rpadchars

(defthm character-listp-of-rpadchars
  (character-listp (rpadchars x len)))

Theorem: len-of-rpadchars

(defthm len-of-rpadchars
  (equal (len (rpadchars x len))
         (max (len x) (nfix len))))

Theorem: charlisteqv-implies-equal-rpadchars-1

(defthm charlisteqv-implies-equal-rpadchars-1
  (implies (charlisteqv x x-equiv)
           (equal (rpadchars x len)
                  (rpadchars x-equiv len)))
  :rule-classes (:congruence))

Theorem: icharlisteqv-implies-icharlisteqv-rpadchars-1

(defthm icharlisteqv-implies-icharlisteqv-rpadchars-1
  (implies (icharlisteqv x x-equiv)
           (icharlisteqv (rpadchars x len)
                         (rpadchars x-equiv len)))
  :rule-classes (:congruence))