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Asciip

Recognizer for ascii.

Function: asciip

(defun asciip (x)
  (declare (xargs :guard t))
  (mbe :logic (unsigned-byte-p 7 x)
       :exec (and (integerp x) (<= 0 x) (< x 128))))

Theorem: booleanp-of-asciip

(defthm booleanp-of-asciip
  (b* ((yes/no (asciip x)))
    (booleanp yes/no))
  :rule-classes :rewrite)

Theorem: asciip-forward-unsigned-byte-p

(defthm asciip-forward-unsigned-byte-p
  (implies (asciip x)
           (unsigned-byte-p 7 x))
  :rule-classes :forward-chaining)

Theorem: unsigned-byte-p-rewrite-asciip

(defthm unsigned-byte-p-rewrite-asciip
  (equal (unsigned-byte-p 7 x)
         (asciip x)))

Theorem: natp-when-asciip

(defthm natp-when-asciip
  (implies (asciip x) (natp x))
  :rule-classes :compound-recognizer)