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, 5 insertions, 2 deletions

diff --git a/lib.h b/lib.h
index dae6c755..e33667a4 100644
--- a/lib.h
+++ b/lib.h
@@ -38,7 +38,7 @@ typedef int_ptr_t cnum;
 #define NUM_MIN (INT_PTR_MIN/4)
 
 typedef enum type {
-  NUM = TAG_NUM, CHR = TAG_CHR, LIT = TAG_LIT, CONS,
+  NIL, NUM = TAG_NUM, CHR = TAG_CHR, LIT = TAG_LIT, CONS,
   STR, SYM, PKG, FUN, VEC, LCONS, LSTR, COBJ, ENV,
   BGNUM
 } type_t;
@@ -216,7 +216,10 @@ INLINE int is_lit(val obj) { return tag(obj) == TAG_LIT; }
 
 INLINE type_t type(val obj)
 {
-  return tag(obj) ? (type_t) tag(obj) : obj->t.type;
+  return obj ? tag(obj) 
+               ? (type_t) tag(obj)
+               : obj->t.type
+             : NIL;
 }
 
 typedef struct wli wchli_t;