diff --git a/parse.lisp b/parse.lisp
index 83b778c..5b45943 100644
--- a/parse.lisp
+++ b/parse.lisp
@@ -90,12 +90,12 @@ proposition."))
   "Return t if STR is only alphabetical characters."
   (not (find-if-not 'alpha-char-p str)))
 
-(defparameter *longest-non-alpha-operator*
+(defparameter *longest-alpha-operator*
   (apply 'max (mapcar
                (lambda (entry)
-                 (apply 'max
+                 (apply 'max 0
                         (mapcar 'length
-                                (remove-if 'alpha-string-p (cdr entry)))))
+                                (remove-if-not 'alpha-string-p (cdr entry)))))
                *operator-symbol-table*))
   "The longest operator in `*operator-symbol-table*' such that `alpha-string-p'
 returns t.")
@@ -224,7 +224,7 @@ a variable."
   "Return the operator symbol for TOKEN, if it is an operator. As a second
 value, return the matched portion of TOKEN. If no match is found, return
 (values nil nil)."
-  (loop for len downfrom (min *longest-non-alpha-operator* (length token)) to 1
+  (loop for len downfrom (min *longest-alpha-operator* (length token)) to 1
         for cur-test = (subseq token 0 len)
         for oper-sym = (operator-symbol cur-test)
         when oper-sym do
@@ -446,7 +446,7 @@ found variables."
              (push-operator value token-pos)))))
       ;; remove implicit-and
       (when (eq 'implicit-and (peek-operator))
-          (pop-operator))
+        (pop-operator))
       (loop for (top-oper . top-pos) = (car operators)
             while top-oper
             when (eq top-oper 'open-paren) do