1 files changed, 3 insertions, 3 deletions
diff --git a/extra.lisp b/extra.lisp
index 3b64096..9805ca0 100644
--- a/extra.lisp
+++ b/extra.lisp
@@ -29,11 +29,11 @@
     `(comp ,(reverse binding-list)
        ,(cons 'list (reverse name-list)))))
 
-(declaim (ftype (function (parser parser parser) parser) within))
-(defun within (left p right)
+(declaim (ftype (function (parser parser &optional parser) parser) within))
+(defun within (left p &optional right)
   (comp ((_ left)
          (cell p)
-         (_ right))
+         (_ (or right left)))
     cell))
 
 (declaim (ftype (function (parser parser) parser) interlinked))