Define an irrelevant value of a type.
Macro:
(defmacro defirrelevant (name &key type body (parents 'nil parents-p) short) (cons 'define (cons name (cons 'nil (cons ':returns (cons (cons 'irr (cons type 'nil)) (append (and parents-p (cons ':parents (cons parents 'nil))) (cons ':short (cons short (cons ':long (cons '(xdoc::topstring (xdoc::p "This can be used as a dummy value of the type.")) (cons body (cons '/// (cons (cons 'in-theory (cons (cons 'disable (cons (cons ':e (cons name 'nil)) 'nil)) 'nil)) 'nil))))))))))))))