1 files changed, 10 insertions, 1 deletions

diff --git a/gui.rkt b/gui.rkt
index 98b4f77..0c465f2 100644
--- a/gui.rkt
+++ b/gui.rkt
@@ -71,13 +71,22 @@
         (lambda (x) (setup-num-btn x bottom-op-panel))
         '(0 "." ^ ))
 
+      (new button%
+           [parent top-op-panel]
+           [label "←"]
+           [callback
+             (lambda (button event)
+               (define str (send msg get-label))
+               (send msg set-label (substring str 0 (- (string-length str) 1))))])
+
 
       (new button%
            [parent bottom-op-panel]
            [label "="]
            [callback
              (lambda (button event)
+               (define ^ expt)
                (send msg set-label (~a
-                       (full-eval (full-parse (send msg get-label))))))])
+                       (eval (full-parse (send msg get-label))))))])
 
       (send frame show #t))