Added error handling and updated example

Author: m-messer

evaluation_function.wl

@@ -16,7 +16,23 @@ processEvaluate[jsonData_] := Module[{result, requestData, answer, response, par
     Print["Evaluating Response Against Answer"];
     result = EvaluationFunction[type, answer, response, params];
     Print["Output: ", result];
-    <| "command" -> "eval", "result" -> result |>
+
+    If[result["error"] != Null,
+      Return[
+      <| "command" -> "eval",
+        "error" -> <|
+          "message" -> result["error"]
+        |>
+      |>
+      ]
+    ];
+
+    <| "command" -> "eval",
+      "result" -> <|
+        "is_correct" -> result["is_correct"],
+        "feedback" -> result["feedback"]
+      |>
+    |>
 ]
 
 processPreview[jsonData_] := Module[{result, requestData, response},
@@ -28,6 +44,16 @@ processPreview[jsonData_] := Module[{result, requestData, response},
     result = PreviewFunction[response];
     Print["Result: ", result];
 
+    If[result["error"] != Null,
+      Return[
+      <| "command" -> "eval",
+        "error" -> <|
+          "message" -> result["error"]
+        |>
+      |>
+      ]
+    ];
+
     <| "command" -> "preview",
       "result" ->
           <|"preview" -> result|>

preview_example.json

@@ -1,6 +1,6 @@
 {
-  "method": "preview",
+  "command": "preview",
   "params": {
-	"response":"Sin[a x + b]"
+	"response":"\\sin{p x}"
 	}
 }

structure_match_example1.json

@@ -1,10 +1,10 @@
 {
-  "method": "eval",
+  "command": "eval",
   "params": {
-    "answer":"Sin[p x + q]",
-	"response":"Sin[a x + b]",
+    "answer":"n!!",
+	"response":"a!!",
 	"params":{
-		"comparisonType":"structure",
+		"type":"structure",
 		"named_variables":"{x}",
 		"correct_response_feedback":"Your answer is correct!",
 		"incorrect_response_feedback":"Your answer is incorrect!"