Fix incorrect parenthesis

eval.lisp

@@ -29,6 +29,21 @@
   (:documentation "Condition representing an error that occurred during
 evaluation for a proposition."))
 
+(defun operator-argument-count (oper)
+  "Return the minimum number of arguments that OPER takes as the first value,
+and the maximum number (or nil for infinity) as a second value."
+  (case oper
+    (and (values 1 nil))
+    (or (values 1 nil))
+    (xor (values 1 nil))
+    (not (values 1 1))
+    (implies (values 2 2))
+    (converse (values 2 2))
+    (iff (values 2 2))
+    (nand (values 1 nil))
+    (nor (values 1 nil))
+    (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