function calling works in theory (can't test yet)

include/ground.h

@@ -336,6 +336,23 @@ struct GroundBytecode {
     GroundBytecodeHeap    heap;
 };
 
+
+// --- Internal Ground components, avoid use outside of Ground ---
+
+enum GroundExecutionResultType {
+    _GER_CONTINUE, _GER_JUMP, _GER_RETURN, _GER_END
+};
+
+struct GroundExecutionResult {
+    enum GroundExecutionResultType type;
+    union {
+        GroundBytecodeValue value;
+        GroundSize line;
+        GroundInt end;
+    } as;
+};
+
+
 // 
 // INTERFACE
 // 
@@ -428,6 +445,8 @@ struct _Ground {
         GroundState       (*State)       (GroundState* in);
 
         GroundIdentifier* (*Identifier) (GroundIdentifier* in);
+
+        GroundBytecodeValue (*BytecodeValue) (GroundBytecodeValue* in);
     } Copy;
 
     struct {
@@ -481,11 +500,11 @@ struct _Ground {
         void         (*save) (GroundBytecode* bytecode, const char* path);
         GroundBytecode (*load) (const char* path);
         struct {
-            void (*execute)  (GroundBytecodeProgram* program, GroundBytecodeHeap* heap);
-            void (*optimise) (GroundBytecodeProgram* program);
+            GroundBytecodeValue (*execute)  (GroundBytecodeProgram* program, GroundBytecodeHeap* heap);
+            void                (*optimise) (GroundBytecodeProgram* program);
         } Program;
         struct {
-            int64_t (*execute) (GroundBytecodeInstruction* instruction, GroundBytecodeHeap* heap);
+            struct GroundExecutionResult (*execute) (GroundBytecodeInstruction* instruction, GroundBytecodeHeap* heap);
         } Instruction;
         struct {
             void         (*set) (GroundBytecodeHeap* heap, GroundSize idx, GroundValue value);