+(let ((truth-map (make-hash-table :test #'equalp)))
+ (dolist (string '("true" "t" "yes" "on" "yup" "verily"))
+ (setf (gethash string truth-map) t))
+ (dolist (string '("false" "nil" "no" "off" "nope" "nowise"))
+ (setf (gethash string truth-map) nil))
+ (defun truishp (string)
+ "Convert STRING to a boolean."
+ (multiple-value-bind (val foundp) (gethash string truth-map)
+ (if foundp val
+ (error "Unrecognized boolean value `~A'" string)))))
+