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Representation-of-integer-operations

Sub-uchar-uchar-okp

Check if the subtraction of a value of type unsigned char and a value of type unsigned char is well-defined.

Definitions and Theorems

Function: sub-uchar-uchar-okp

(defun sub-uchar-uchar-okp (x y)
  (declare (xargs :guard (and (ucharp x) (ucharp y))))
  (sub-sint-sint-okp (sint-from-uchar x)
                     (sint-from-uchar y)))

Theorem: booleanp-of-sub-uchar-uchar-okp

(defthm booleanp-of-sub-uchar-uchar-okp
  (booleanp (sub-uchar-uchar-okp x y)))

Theorem: sub-uchar-uchar-okp-of-uchar-fix-x

(defthm sub-uchar-uchar-okp-of-uchar-fix-x
  (equal (sub-uchar-uchar-okp (uchar-fix x) y)
         (sub-uchar-uchar-okp x y)))

Theorem: sub-uchar-uchar-okp-uchar-equiv-congruence-on-x

(defthm sub-uchar-uchar-okp-uchar-equiv-congruence-on-x
  (implies (uchar-equiv x x-equiv)
           (equal (sub-uchar-uchar-okp x y)
                  (sub-uchar-uchar-okp x-equiv y)))
  :rule-classes :congruence)

Theorem: sub-uchar-uchar-okp-of-uchar-fix-y

(defthm sub-uchar-uchar-okp-of-uchar-fix-y
  (equal (sub-uchar-uchar-okp x (uchar-fix y))
         (sub-uchar-uchar-okp x y)))

Theorem: sub-uchar-uchar-okp-uchar-equiv-congruence-on-y

(defthm sub-uchar-uchar-okp-uchar-equiv-congruence-on-y
  (implies (uchar-equiv y y-equiv)
           (equal (sub-uchar-uchar-okp x y)
                  (sub-uchar-uchar-okp x y-equiv)))
  :rule-classes :congruence)