Better eval.lisp

eval.lisp

@@ -45,31 +45,20 @@ and the maximum number (or nil for infinity) as a second value."
     (t (error "unknown operator: ~S" oper))))
 
 (defun logical-xor (&rest args)
-  "Logical xor (not equal) each argument in turn with its following argument.
-NOTE: This is NOT a macro, there is no short circuit evaluation (all arguments
-are evaluated no matter what)."
-  (loop with result = nil
-        for arg in args do
-          (setq result (not (eq result arg)))
-        finally (return result)))
+  "Logical xor (not equal) each argument in turn with its following argument."
+  (eql 1 (count-if #'identity args)))
 
 (defun logical-and (&rest args)
-  "Logical and (all true).
-NOTE: This is NOT a macro, there is no short circuit evaluation (all arguments
-are evaluated no matter what)."
-  (not (member nil args)))
+  "Logical and (all true)."
+  (every #'identity args))
 
 (defun logical-or (&rest args)
-  "Logical or (one or more true).
-NOTE: This is NOT a macro, so there is no short circuit evaluation (all
-arguments are evaluated no matter what)."
-  (not (not (member t args))))
+  "Logical or (one or more true)."
+  (some #'identity args))
 
 (defun logical-implies (prop1 prop2)
   "Evaluate the logical implies operation on PROP1 and PROP2. That is \"if
-PROP1, then PROP2\".
-NOTE: This is NOT a macro, so there is no short circuit evaluation (all
-arguments are evaluated no matter what)."
+PROP1, then PROP2\"."
   (if prop1 ;; only if first is true
       prop2 ;; eval second
       t)) ;; otherwise, just return true