new feature: defstruct clause macros.

* lisplib.c (struct_set_entries): Trigger autoload on new
symbols define-struct-clause and *struct-clause-expander*.

* stdlib/struct.tl (*struct-clause-expander*): New variable.
(defstruct): expand-slot local function now returns list of
expanded slots, not a single slot; every case in the tree-case
is converted to return a list. The syntax of a slot clause is
first expanded through *struct-clause-expander hash; if that
works then the resulting list is further scanned for
expansions.
(define-struct-clause): New macro.
(:delegate): New struct clause defined with
define-struct-clause. Provides single-slot delegation.

* tests/012/oop.tl: Tests for :delegate.

* txr.1: Documented define-struct-clause and :delegate.

* stdlib/doc-syms.tl: Updated.

1 files changed, 15 insertions, 0 deletions

diff --git a/tests/012/oop.tl b/tests/012/oop.tl
index bab4ab68..a5c57973 100644
--- a/tests/012/oop.tl
+++ b/tests/012/oop.tl
@@ -93,3 +93,18 @@
     (new* type a 3 b 4)) #S(ab a 3 b 4)
   (let ((type (find-struct-type 'ab)))
     (new* (type 3 4))) #S(ab a 3 b 4))
+
+(defstruct worker ()
+  name
+  (:method work (me) `worker @{me.name} works`)
+  (:method relax (me : (min 15)) `worker @{me.name} relaxes for @min min`))
+
+(defstruct contractor ()
+  sub
+  (:delegate work (me) me.sub.sub)
+  (:delegate break (me : min) me.sub.sub relax))
+
+(let ((co (new contractor sub (new contractor sub (new worker name "foo")))))
+  (mtest co.(work) "worker foo works"
+         co.(break) "worker foo relaxes for 15 min"
+         co.(break 5) "worker foo relaxes for 5 min"))