+(let ((truish '("true" "t" "yes" "verily"))
+ (falsish '("false" "nil" "no" "nowise")))
+ (defun truishp (string)
+ "Convert STRING to a boolean."
+ (cond ((member string truish :test #'string=) t)
+ ((member string falsish :test #'string=) nil)
+ (t (error "Unrecognized boolean value `~A'" string)))))
+