builtin variables

include/lang2/builtins.x.h

 // X macro: Define a macro named X, then include this file, then undef X.
 
+#ifdef Y
+Y("none", knone)
+Y("true", ktrue)
+Y("false", kfalse)
+#endif
+
 #ifdef X
 X("+", l2_builtin_add)
 X("-", l2_builtin_sub)

include/lang2/vm/vm.h

 
 	struct l2_vm_stack_frame fstack[1024];
 	l2_word fsptr;
+
+	l2_word knone, ktrue, kfalse;
 };
 
 void l2_vm_init(struct l2_vm *vm, l2_word *ops, size_t opcount);

lib/gen/gen.c

 	l2_bufio_writer_init(&gen->writer, w);
 
 	// Register atoms for all builtins
+#define Y(name, k) \
+	l2_strset_put_copy(&gen->atomset, name);
 #define X(name, f) \
 	l2_strset_put_copy(&gen->atomset, name);
 #include "builtins.x.h"
+#undef Y
 #undef X
 }
 

lib/vm/builtins.c

 			break;
 
 		case L2_VAL_TYPE_ATOM:
-			l2_io_printf(out, "(atom %u)", val->atom);
+			if (val->atom == vm->values[vm->ktrue].atom) {
+				l2_io_printf(out, "(true)");
+			} else if (val->atom == vm->values[vm->kfalse].atom) {
+				l2_io_printf(out, "(false)");
+			} else {
+				l2_io_printf(out, "(atom %u)", val->atom);
+			}
 			break;
 
 		case L2_VAL_TYPE_REAL:

lib/vm/vm.c

 	// Define a C function variable for every builtin
 	l2_word id;
 	l2_word key = 1;
+#define Y(name, k) \
+	if (strcmp(#k, "knone") == 0) { \
+		id = 0; \
+	} else { \
+		id = alloc_val(vm); \
+		vm->values[id].flags = L2_VAL_TYPE_ATOM | L2_VAL_CONST; \
+		vm->values[id].atom = key; \
+	} \
+	vm->k = id; \
+	l2_vm_namespace_set(&vm->values[builtins], key++, id);
 #define X(name, f) \
 	id = alloc_val(vm); \
-	vm->values[id].flags = L2_VAL_TYPE_CFUNCTION; \
+	vm->values[id].flags = L2_VAL_TYPE_CFUNCTION | L2_VAL_CONST; \
 	vm->values[id].cfunc = f; \
 	l2_vm_namespace_set(&vm->values[builtins], key++, id);
 #include "builtins.x.h"