Throw error on wrong number of arguments

1 files changed, 9 insertions, 6 deletions

diff --git a/src/main/java/org/zwobble/couscous/values/StringValue.java b/src/main/java/org/zwobble/couscous/values/StringValue.java
index da45f02..2d4bf17 100644
--- a/src/main/java/org/zwobble/couscous/values/StringValue.java
+++ b/src/main/java/org/zwobble/couscous/values/StringValue.java
@@ -1,18 +1,21 @@
 package org.zwobble.couscous.values;
 
+import static java.util.Arrays.asList;
+
 import lombok.Value;
 import lombok.val;
 
 @Value
 public class StringValue implements InterpreterValue {
     private static final ConcreteType<?> TYPE = ConcreteType.<StringValue>builder()
-        .method("length", (receiver, arguments) -> new IntegerValue(receiver.value.length()))
+        .method("length", asList(), (receiver, arguments) -> new IntegerValue(receiver.value.length()))
         
-        .method("substring", (receiver, arguments) -> {
-            val startIndex = arguments.pop(IntegerValue.class);
-            val endIndex = arguments.pop(IntegerValue.class);
-            return new StringValue(receiver.value.substring(startIndex.getValue(), endIndex.getValue()));
-        })
+        .method("substring", asList(IntegerValue.TYPE, IntegerValue.TYPE),
+            (receiver, arguments) -> {
+                val startIndex = (IntegerValue)arguments.get(0);
+                val endIndex = (IntegerValue)arguments.get(1);
+                return new StringValue(receiver.value.substring(startIndex.getValue(), endIndex.getValue()));
+            })
         
         .build();