Recognize the extended source characters.
(ext-source-charp x) → yes/no
These are the non-basic source-characters.
Function:
(defun ext-source-charp (x) (declare (xargs :guard t)) (let ((__function__ 'ext-source-charp)) (declare (ignorable __function__)) (and (source-charp x) (not (basic-source-charp x)))))
Theorem:
(defthm booleanp-of-ext-source-charp (b* ((yes/no (ext-source-charp x))) (booleanp yes/no)) :rule-classes :rewrite)
Theorem:
(defthm source-charp-alt-def (equal (source-charp x) (or (basic-source-charp x) (ext-source-charp x))))