src/Main.elm

@@ -14,6 +14,7 @@ type alias Model =
     { stack : List Float
     , currentNum : String
     , error : Maybe String
+    , dirty : Bool
     }
 
 
@@ -22,6 +23,7 @@ initialModel =
     { stack = []
     , currentNum = "0"
     , error = Nothing
+    , dirty = False
     }
 
 
@@ -103,7 +105,7 @@ update msg model =
             initialModel
 
         Clear ->
-            { model | currentNum = "0" }
+            { model | currentNum = "0", dirty = False }
 
         Back ->
             let
@@ -129,7 +131,7 @@ update msg model =
                     { model | error = Just "PARSE ERR" }
 
                 Just num ->
-                    { model | stack = num :: model.stack, currentNum = "0" }
+                    { model | stack = num :: model.stack, dirty = True }
 
         InputOperator operator ->
             case model.stack of
@@ -156,12 +158,16 @@ update msg model =
                             { model
                                 | stack = xs
                                 , currentNum = String.fromFloat newNum
+                                , dirty = True
                             }
 
         InputNumber num ->
             if model.currentNum == "0" then
                 { model | currentNum = String.fromFloat num }
 
+            else if model.dirty then
+                { model | currentNum = String.fromFloat num, dirty = False }
+
             else
                 { model | currentNum = model.currentNum ++ String.fromFloat num }
 
@@ -241,7 +247,16 @@ section =
         , cell (onClick <| InputNumber 0) Single White "0"
         , cell (onClick SetDecimal) Single White "."
         , cell (onClick SetSign) Single White "+/-"
-        , cell (onClick <| Enter) Single Yellow "Enter"
+        , cell (onClick <| Enter) Single Yellow "↵"
+        ]
+
+
+emptyBox : Html Msg
+emptyBox =
+    div
+        [ class "input-box"
+        ]
+        [ span [ class "empty" ] [ text "empty" ]
         ]
 
 
@@ -269,7 +284,8 @@ view model =
         [ h1 [ class "h1" ] [ text "RPN Calculator" ]
         , div
             [ class "calculator" ]
-            (List.map stackBox (List.reverse model.stack)
+            (List.repeat (3 - List.length model.stack) emptyBox
+                ++ List.map stackBox (List.reverse <| List.take 3 model.stack)
                 ++ [ inputBox <|
                         case model.error of
                             Nothing ->
@@ -280,7 +296,8 @@ view model =
                    , section
                    ]
             )
-        , div [] [ text <| Debug.toString model ]
+
+        -- , div [] [ text <| Debug.toString model ]
         ]
 
 

style.css

@@ -26,6 +26,10 @@ body {
     margin: auto;
 }
 
+.empty {
+    opacity: 0;
+}
+
 .input-box {
     text-align: right;
     padding: 12px;