diff --git a/src/main.rs b/src/main.rs
index 6ab86e5..d49a190 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -3,7 +3,7 @@ struct VM<'p> {
     block: u32, ip: u32, 
     heap: Heap<'p>,
     locals: Object,
-    stack: Vec<StackItem>, 
+    stack: Vec<Value>, 
     status: Status 
 }
 
@@ -16,18 +16,18 @@ enum Status {
 }
 
 #[derive(Clone, Copy, Debug)]
-enum StackItem {
+enum Value {
     Object(Object),
     Integer(u32),
 }
-impl StackItem {
+impl Value {
     fn object(self) -> Option<Object> {
-        if let StackItem::Object(t) = self { return Some(t) }
+        if let Value::Object(t) = self { return Some(t) }
         return None
     }
     
     fn integer(self) -> Option<u32> {
-        if let StackItem::Integer(u) = self { return Some(u) }
+        if let Value::Integer(u) = self { return Some(u) }
         return None
     }
 }
@@ -193,20 +193,20 @@ impl<'p> VM<'p> {
 
         match instruction {
             &Instruction::PushNull => {
-                self.stack.push(StackItem::Object(NULL))
+                self.stack.push(Value::Object(NULL))
             }
 
             &Instruction::PushInteger(int) => {
-                self.stack.push(StackItem::Integer(int))
+                self.stack.push(Value::Integer(int))
             }
 
             &Instruction::PushNew(ty) => {
                 let t = self.heap.object_create(ty);
-                self.stack.push(StackItem::Object(t))
+                self.stack.push(Value::Object(t))
             }
 
             Instruction::PushLocals => {
-                self.stack.push(StackItem::Object(self.locals))
+                self.stack.push(Value::Object(self.locals))
             }
             
             Instruction::PopLocals => {
@@ -264,7 +264,7 @@ impl<'p> VM<'p> {
 }
 
 impl Op11 {
-    fn perform(&self, heap: &mut Heap, v0: StackItem) -> Result<StackItem, &'static str> {
+    fn perform(&self, heap: &mut Heap, v0: Value) -> Result<Value, &'static str> {
         match self {
             &Op11::Get(ix) => {
                 let t0 = v0.object().ok_or("must be a object")?;
@@ -276,12 +276,12 @@ impl Op11 {
 }
 
 impl Op21 {
-    fn perform(&self, heap: &mut Heap, v0: StackItem, v1: StackItem) -> Result<StackItem, &'static str> {
+    fn perform(&self, heap: &mut Heap, v0: Value, v1: Value) -> Result<Value, &'static str> {
         match self {
             Op21::Add => {
                 let i0 = v0.integer().ok_or("must be an integer")?;
                 let i1 = v1.integer().ok_or("must be an integer")?;
-                Ok(StackItem::Integer(i0.wrapping_add(i1)))
+                Ok(Value::Integer(i0.wrapping_add(i1)))
             }
             &Op21::Set(ix) => {
                 let t0 = v0.object().ok_or("must be a object")?;
@@ -329,7 +329,7 @@ struct Heap<'p> {
 #[derive(Debug)]
 enum HeapItem {
     Type(Type),
-    StackItem(StackItem),
+    Value(Value),
 }
 
 #[derive(Clone, Copy, Debug, PartialEq, Eq)]
@@ -357,7 +357,7 @@ impl<'p> Heap<'p> {
         let index = self.data.len() as u32;
         self.data.push(HeapItem::Type(ty));
         for _ in 0..td.len {
-            self.data.push(HeapItem::StackItem(StackItem::Object(NULL)));
+            self.data.push(HeapItem::Value(Value::Object(NULL)));
         }
         Object { index }
     }
@@ -371,28 +371,28 @@ impl<'p> Heap<'p> {
         }
     }
 
-    fn object_get_arg(&self, object: Object, ix: u32) -> StackItem {
+    fn object_get_arg(&self, object: Object, ix: u32) -> Value {
         let ty = self.object_get_type(object);
         let td = self.program.type_get(ty);
 
         if ix < td.len {
             let value = self.data.get((object.index + ix + 1) as usize).expect("should have been present");
             match value {
-                &HeapItem::StackItem(si) => si,
-                _ => panic!("should have been a StackItem")
+                &HeapItem::Value(si) => si,
+                _ => panic!("should have been a Value")
             }
         } else {
             panic!("invalid ix: {}", ix)
         }
     }
 
-    fn object_set_arg(&mut self, object: Object, ix: u32, arg: StackItem) {
+    fn object_set_arg(&mut self, object: Object, ix: u32, arg: Value) {
         let ty = self.object_get_type(object);
         let td = self.program.type_get(ty);
 
         if ix < td.len {
             let slot = self.data.get_mut((object.index + ix + 1) as usize).expect("should have been present");
-            *slot = HeapItem::StackItem(arg)
+            *slot = HeapItem::Value(arg)
         } else {
             panic!("invalid ix: {}", ix)
         }