begin while repeat

loops.forth

@@ -0,0 +1,5 @@
+: test1 begin dup while 1 - dup . repeat ;
+10 test1
+
+: test2 begin 1 - dup . dup 0= until ;
+10 test2

src/fh_builtins.c

@@ -82,8 +82,8 @@ static enum fh_error w_minus(struct fh_thread_s *fh, const struct fh_word_s *w)
   (void) w;
   enum fh_error rv;
   uint32_t a = 0, b = 0;
-  TRY(ds_pop(fh, &a));
   TRY(ds_pop(fh, &b));
+  TRY(ds_pop(fh, &a));
   TRY(ds_push(fh, a - b));
   return FH_OK;
 }
@@ -778,7 +778,6 @@ static enum fh_error w_then(struct fh_thread_s *fh, const struct fh_word_s *w)
 {
   (void) w;
   enum fh_error rv;
-  struct fh_instruction_s instr;
 
   ENSURE_STATE(FH_STATE_COMPILE);
 
@@ -794,6 +793,76 @@ static enum fh_error w_then(struct fh_thread_s *fh, const struct fh_word_s *w)
   return FH_OK;
 }
 
+static enum fh_error w_until(struct fh_thread_s *fh, const struct fh_word_s *w)
+{
+  (void) w;
+  enum fh_error rv;
+  struct fh_instruction_s instr;
+
+  ENSURE_STATE(FH_STATE_COMPILE);
+
+  uint32_t destaddr = 0;
+  TRY(cs_pop(fh, &destaddr));
+
+  instr_init(&instr, FH_INSTR_JUMPZERO, destaddr);
+  TRY(fh_compile_put(fh, &instr, INSTR_SIZE));
+  return FH_OK;
+}
+
+static enum fh_error w_begin(struct fh_thread_s *fh, const struct fh_word_s *w)
+{
+  (void) w;
+  enum fh_error rv;
+  ENSURE_STATE(FH_STATE_COMPILE);
+  TRY(cs_push(fh, fh->compile_top)); /* dest */
+  return FH_OK;
+}
+
+static enum fh_error w_while(struct fh_thread_s *fh, const struct fh_word_s *w)
+{
+  (void) w;
+  enum fh_error rv;
+  struct fh_instruction_s instr;
+
+  ENSURE_STATE(FH_STATE_COMPILE);
+
+  uint32_t destaddr = 0;
+  TRY(cs_pop(fh, &destaddr));
+
+  TRY(cs_push(fh, fh->compile_top)); // orig
+  TRY(cs_push(fh, destaddr)); // dest
+
+  instr_init(&instr, FH_INSTR_JUMPZERO, MAGICADDR_UNRESOLVED);
+  TRY(fh_compile_put(fh, &instr, INSTR_SIZE));
+  return FH_OK;
+}
+
+static enum fh_error w_repeat(struct fh_thread_s *fh, const struct fh_word_s *w)
+{
+  (void) w;
+  enum fh_error rv;
+  struct fh_instruction_s instr;
+
+  ENSURE_STATE(FH_STATE_COMPILE);
+
+  uint32_t origaddr = 0;
+  uint32_t destaddr = 0;
+  TRY(cs_pop(fh, &destaddr));
+  TRY(cs_pop(fh, &origaddr));
+
+  struct fh_instruction_s *branch_instr = (void *) &fh->compile[origaddr];
+  if (branch_instr->data != MAGICADDR_UNRESOLVED) {
+    LOGE("REPEAT control stack corruption");
+    return FH_ERR_INTERNAL;
+  }
+  branch_instr->data = fh->compile_top + INSTR_SIZE;
+
+  instr_init(&instr, FH_INSTR_JUMP, destaddr);
+  TRY(fh_compile_put(fh, &instr, INSTR_SIZE));
+
+  return FH_OK;
+}
+
 static enum fh_error wp_setbase(struct fh_thread_s *fh, const struct fh_word_s *w)
 {
   fh_setbase(fh, w->param);
@@ -998,12 +1067,16 @@ enum fh_error register_builtin_words(struct fh_thread_s *fh)
       {"if",        w_if,              1, 0},
       {"else",      w_else,            1, 0},
       {"then",      w_then,            1, 0},
+      {"recurse",   w_recurse,         1, 0},
+      {"begin",     w_begin,           1, 0},
+      {"while",     w_while,           1, 0},
+      {"repeat",    w_repeat,          1, 0},
+      {"until",     w_until,           1, 0},
       /* Syntax */
       {":",         w_colon,           0, 0},
       {";",         w_semicolon,       1, 0},
       {"\\",        w_backslash,       1, 0}, // line comment
       {"(",         w_paren,           1, 0}, // enclosed comment
-      {"recurse",   w_recurse,         1, 0},
       {"reset",     w_reset,           1, 0},
       {"immediate", w_immediate,       1, 0},
       {"postpone",  w_postpone,        1, 0},