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Std/system/function-queries

Definedp

Check if a named logic-mode function is defined.

Signature
(definedp fn wrld) → yes/no
Arguments: fn — Guard (symbolp fn).; wrld — Guard (plist-worldp wrld).
Returns: yes/no — Type (booleanp yes/no).

We check if the function symbol has an unnormalized-body property.

The built-in program-mode functions are defined but do not have an unnormalized-body property. This is why this utility should only be used on logic-mode functions.

See definedp+ for an enhanced variant of this utility.

Definitions and Theorems

Function: definedp

(defun definedp (fn wrld)
  (declare (xargs :guard (and (symbolp fn) (plist-worldp wrld))))
  (let ((__function__ 'definedp))
    (declare (ignorable __function__))
    (if (getpropc fn 'unnormalized-body
                  nil wrld)
        t
      nil)))

Theorem: booleanp-of-definedp

(defthm booleanp-of-definedp
  (b* ((yes/no (definedp fn wrld)))
    (booleanp yes/no))
  :rule-classes :rewrite)