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Sign

Sign-kind

Get the kind (tag) of a sign structure.

Signature
(sign-kind x) → kind
Arguments: x — Guard (signp x).

Definitions and Theorems

Function: sign-kind$inline

(defun sign-kind$inline (x)
  (declare (xargs :guard (signp x)))
  (let ((__function__ 'sign-kind))
    (declare (ignorable __function__))
    (mbe :logic (cond ((or (atom x) (eq (car x) :plus)) :plus)
                      (t :minus))
         :exec (car x))))

Theorem: sign-kind-possibilities

(defthm sign-kind-possibilities
 (or (equal (sign-kind x) :plus)
     (equal (sign-kind x) :minus))
 :rule-classes ((:forward-chaining :trigger-terms ((sign-kind x)))))