lib: access special methods via special slot mechanism.

* ffi.c (ffi_flex_struct_in): Use get_special_slot to obtain
length method.

* lib.c (nullify_s, from_list_s, lambda_set_s): Definitions
removed from here.
(seq_info, car, cdr,  rplaca, rplacd, make_like, nullify,
replace_obj, length, empty, sub, ref, refset, dwim_set): Use
get_special_slot to obtain special method from object,
rather than maybe_slot.
(obj_init): Remove initializations of nullify_s, from_list_s
and lambda_set_s from here.

* struct.c (enum special_slot): Definition removed from here.
(nullify_s, from_list_s, lambda_set_s): Definitions moved here
from lib.c.
(special_sym): New static array.
(struct_init): Initializations of nullify_s, from_list_s
and lambda_set_s moved here from lib.c.
(get_special_slot): New function.

* struct.h (lambda_set_s): Declared.
(enum special_slot): Definition moved here.
(get_special_slot): Declared.

* txr.1: Added compat note, since get_special_slot behaves
like maybe_slot under 224 compatibility.

1 files changed, 19 insertions, 5 deletions

diff --git a/struct.c b/struct.c
index b38487c0..87ea9b96 100644
--- a/struct.c
+++ b/struct.c
@@ -72,11 +72,6 @@ struct stslot {
 #define stslot_loc(s) mkloc(*(s)->home, (s)->home_type)
 #define stslot_place(s) (*(s)->home)
 
-enum special_slot {
-  equal_meth,
-  num_special_slots
-};
-
 struct struct_type {
   val self;
   val name;
@@ -107,6 +102,13 @@ val struct_type_s, meth_s, print_s, make_struct_lit_s;
 val init_k, postinit_k;
 val slot_s, derived_s;
 
+val nullify_s, from_list_s, lambda_set_s;
+
+static val *special_sym[num_special_slots] = {
+  &equal_s, &nullify_s, &from_list_s, &lambda_s, &lambda_set_s,
+  &length_s, &car_s, &cdr_s, &rplaca_s, &rplacd_s
+};
+
 static val struct_type_hash;
 static val slot_hash;
 static val struct_type_finalize_f;
@@ -135,6 +137,9 @@ void struct_init(void)
   postinit_k = intern(lit("postinit"), keyword_package);
   slot_s = intern(lit("slot"), user_package);
   derived_s = intern(lit("derived"), user_package);
+  nullify_s = intern(lit("nullify"), user_package);
+  from_list_s = intern(lit("from-list"), user_package);
+  lambda_set_s = intern(lit("lambda-set"), user_package);
   struct_type_hash = make_hash(nil, nil, nil);
   slot_hash = make_hash(nil, nil, t);
   slot_type_hash = make_hash(nil, nil, nil);
@@ -1759,6 +1764,15 @@ val static_slot_type_reg(val slot, val strct)
   return slot;
 }
 
+val get_special_slot(val obj, enum special_slot spidx)
+{
+  val slot = *special_sym[spidx];
+  if (opt_compat && opt_compat <= 224)
+    return maybe_slot(obj, slot);
+  struct struct_inst *si = coerce(struct struct_inst *, obj->co.handle);
+  return get_special_static_slot(si->type, spidx, slot);
+}
+
 static_def(struct cobj_ops struct_type_ops =
            cobj_ops_init(eq, struct_type_print, struct_type_destroy,
                          struct_type_mark, cobj_eq_hash_op));