refactor objects

internal/object/int.go

@@ -18,10 +18,15 @@ func (i Integer) Inspect() string {
 	return fmt.Sprintf("%d", i.Value)
 }
 
-func (i Integer) Clone() Object {
+func (i Integer) Copy() Object {
 	return Integer{Value: i.Value}
 }
 
+// Hash implements the Hasher interface
+func (i Integer) Hash() HashKey {
+	return HashKey{Type: i.Type(), Value: uint64(i.Value)}
+}
+
 func (i Integer) String() string {
 	return i.Inspect()
 }