structs: improve access to initfun and postinitfun.

In this change, a struct type's initfun and postinitfun
become mutable. This is achieved by modeling them as
the pseudo-static-slots :initfun and :postinitfun.
Effectively these now behave as reserved names which do not
denote static slots but these special functions.

* eval.c (lookup_fun): When (meth type slot) syntax is
encountered, treat the slot names :init and :postinit
specially: retrieve these special functions instead of
accessing static slots.

* share/txr/stdlib/place.tl (sys:get-fun-getter-setter):
Similarly, when handling (meth type slot) syntax, return
the alternative getter/setter functions for the special
functions, not the static slot accessing functions.
Also, getting rid of a useless @1 here in existing code,
since (op foo @1) is equivalent to (op foo).

* share/txr/stdlib/struct.tl (sys:defmeth): Check for
the special names :init and :postinit, handling these
through the appropriate setter functions rather than
static-slot-ensure.

* struct.c (init_k, postinit_k): New keyword symbol variables.
(struct_init): Initialize init_k and postinit_k. Register
intrinsics struct-get-initfun, struct-set-initfun,
struct-get-postinitfun and struct-set-postinitfun.
* (struct_get_initfun, struct_set_initfun,
struct_get_postinitfun, struct_set_postinitfun): New
functions.
(method_name): For each struct type visited, check
whether the function is the initfun or postinitfun
and return the appropriate meth syntax if so.

* struct.h (init_k, postinit_k, struct_get_initfun,
struct_set_initfun, struct_get_postinitfun,
struct_set_postinitfun): Declared.

* txr.1: Documented. Updated description of method-name,
defmeth, and documented new functions.

1 files changed, 5 insertions, 0 deletions

diff --git a/struct.h b/struct.h
index e558745f..cab0799d 100644
--- a/struct.h
+++ b/struct.h
@@ -26,12 +26,17 @@
  */
 
 extern val struct_type_s, meth_s, print_s, make_struct_lit_s;
+extern val init_k, postinit_k;
 extern val slot_s, static_slot_s;
 val make_struct_type(val name, val super,
                      val static_slots, val slots,
                      val static_initfun, val initfun, val boactor,
                      val postinitfun);
 val struct_type_p(val obj);
+val struct_get_initfun(val type);
+val struct_set_initfun(val type, val fun);
+val struct_get_postinitfun(val type);
+val struct_set_postinitfun(val type, val fun);
 val super(val type);
 val make_struct(val type, val plist, struct args *);
 val struct_from_plist(val type, struct args *plist);