More refactoring trying to get this cleaned up while trying to keep it easy(ish) to extend for later chapters. I'll never take namespaces for granted again...

interpreter.h

@@ -4,8 +4,15 @@
 #include "expr.h"
 #include "token.h"
 
+typedef enum {
+    INS_STRING,
+    INS_DOUBLE,
+    INS_BOOLEAN,
+    INS_NULL
+} ObjectInstanceType;
+
 typedef struct Object {
-    TokenType instance;
+    ObjectInstanceType instance;
     union {
         char* string;
         double number;
@@ -15,6 +22,6 @@ typedef struct Object {
 
 const void* VisitLiteralExpression(Expr*);
 void* VisitGroupingExpression(Expr*);
-void* VisitBinaryExpression(Expr*);
+Object* VisitBinaryExpression(Expr*);
 
 #endif