Changing type function to not blow up on nil, which makes a lot of code

simpler. A pseudo type code is introduced called NIL with value 0.

* lib.h (enum type): New enumeration value, NIL.
(type): Function accepts object nil and maps it to code NIL.

* eval.c (dwim_loc, op_dwim): test for nil obj and goto hack is gone,
just handle NIL in the switch.

* gc.c (make_obj, mark): Handle new NIL type code in switch.

* hash.c (equal_hash): Handle NIL in the switch instead of nil test.

* lib.c (code2type): Map new NIL type code to null.
(typeof, typecheck): Code simplified.
(class_check, car): Move nil test into switch.
(eql, equal, consp, bignump, stringp, lazy_stringp,
symbolp, functionp, vectorp, cobjp): Simplified.
(length, sub, ref, refset, replace, obj_print, obj_pprint): Handle NIL
in switch instead of nil test.  goto hack removed from refset.

* match.c (do_match_line, do_output_line): switch condition simplified.

* regex.c (regexp): Simplified.
(regex_nfa): Assert condition simplified.

1 files changed, 3 insertions, 7 deletions

diff --git a/eval.c b/eval.c
index 6cb8721e..fcce0b2f 100644
--- a/eval.c
+++ b/eval.c
@@ -751,9 +751,6 @@ static val *dwim_loc(val form, val env, val op, val newform, val *retval)
   val obj = eval_lisp1(second(form), env, form);
   val args = eval_args_lisp1(rest(rest(form)), env, form);
 
-  if (!obj)
-    goto list;
-
   switch (type(obj)) {
   case LIT:
   case STR:
@@ -839,9 +836,9 @@ static val *dwim_loc(val form, val env, val op, val newform, val *retval)
         return vecref_l(obj, index);
       }
     }
+  case NIL:
   case CONS:
   case LCONS:
-  list:
     if (rest(args))
       eval_error(form, lit("[~s ...]: list indexing needs one arg"),
                  obj, nao);
@@ -1102,10 +1099,9 @@ static val op_dwim(val form, val env)
   val obj = eval_lisp1(second(form), env, form);
   val args = eval_args_lisp1(rest(rest(form)), env, form);
 
-  if (!obj)
-    return nil;
-
   switch (type(obj)) {
+  case NIL:
+    return nil;
   case LIT:
   case STR:
   case LSTR: