implement IF-THEN-ELSE

include/fh_runtime.h

@@ -28,16 +28,21 @@ enum fb_instruction_kind {
 
   /* Data = numeric value to push onto the data stack */
   FH_INSTR_NUMBER,
-};
 
-/** Bytecode word indices that are not in the dict, have special effect */
-enum compiler_word {
   /** End of a user defined word, pop address and jump back */
-  CPLWORD_ENDWORD = DICT_SIZE + 1,
+  FH_INSTR_ENDWORD,
+
   /** This is the `s"` instruction, the length (u32) and string data immediately follow */
-  CPLWORD_ALLOCSTR,
+  FH_INSTR_ALLOCSTR,
+
   /** This is the `."` instruction, same format as above. */
-  CPLWORD_TYPESTR,
+  FH_INSTR_TYPESTR,
+
+  /* Unconditional jump */
+  FH_INSTR_JUMP,
+
+  /* Jump if zero */
+  FH_INSTR_JUMPZERO,
 };
 
 /** One instruction in bytecode */
@@ -160,7 +165,8 @@ enum fh_error w_user_word(struct fh_thread_s *fh, const struct fh_word_s *w);
 
 // SFR and magic addresses are "negative"
 #define MAGICADDR_INTERACTIVE 0xFFFFFFFFULL
-#define MAGICADDR_BASE 0xFFFBA5EFULL
+#define MAGICADDR_BASE        0xFFFFBA5EULL
+#define MAGICADDR_UNRESOLVED  0xFFFFFBADULL
 
 /** Get a value rounded up to multiple of word size */
 #define WORDALIGNED(var) (((var) + 3) & ~3)