Implement untupling and use more general append instead of ConvertedImageFilename

byg/src/Evaluation/Function.hs

@@ -6,6 +6,9 @@ import Types (Function(..), Value(..))
 
 evalFunction :: Function -> Value -> Value
 evalFunction f x = case (f, x) of
+  (AppendStrings, Tuple (String _, String _)) ->
+    String undefined
+
   (JoinPaths, Tuple (String _, String _)) ->
     String undefined
 
@@ -15,9 +18,6 @@ evalFunction f x = case (f, x) of
   (IsImageExtension, String _) ->
     Bool undefined
 
-  (ConvertedImageFilename, String _) ->
-    String undefined
-
   (ApplyTemplate, Tuple (Template _, String _)) ->
     String undefined