From d212fc6284a6b7858da4570ef4d22cb88eec747a Mon Sep 17 00:00:00 2001
From: Kaz Kylheku <kaz@kylheku.com>
Date: Fri, 16 Jun 2017 06:40:49 -0700
Subject: Support ref, refset on structs via lambda, lambda-set.

* lib.c (ref, refset): Check for lambda and lambda-set,
respectively, and use it.

* txr.1: Documented.

* tests/012/aseq.tl (add lambda): Fix previously unused
broken method which now causes test to go into infinite
recursion.
---
 lib.c             | 11 +++++++++++
 tests/012/aseq.tl |  2 +-
 txr.1             | 18 ++++++++++++++++++
 3 files changed, 30 insertions(+), 1 deletion(-)

diff --git a/lib.c b/lib.c
index 800142a2..bb5e7e51 100644
--- a/lib.c
+++ b/lib.c
@@ -9246,6 +9246,11 @@ val ref(val seq, val ind)
       return gethash(seq, ind);
     if (seq->co.cls == carray_s)
       return carray_ref(seq, ind);
+    if (structp(seq)) {
+      val lambda_meth = maybe_slot(seq, lambda_s);
+      if (lambda_meth)
+        return funcall2(lambda_meth, seq, ind);
+    }
     /* fallthrough */
   case CONS:
   case LCONS:
@@ -9283,6 +9288,12 @@ val refset(val seq, val ind, val newval)
       return sethash(seq, ind, newval);
     if (seq->co.cls == carray_s)
       return carray_refset(seq, ind, newval);
+    if (structp(seq)) {
+      val lambda_set_meth = maybe_slot(seq, lambda_set_s);
+      if (lambda_set_meth)
+        return funcall3(lambda_set_meth, seq, ind, newval);
+    }
+    /* fallthrough */
   default:
     type_mismatch(lit("ref: ~s is not a sequence"), seq, nao);
   }
diff --git a/tests/012/aseq.tl b/tests/012/aseq.tl
index 7901c4ab..fc6cf76b 100644
--- a/tests/012/aseq.tl
+++ b/tests/012/aseq.tl
@@ -5,7 +5,7 @@
   (:method cdr (me) (if (cdr me.list) (new (add me.n (cdr me.list)))))
   (:method car (me) (+ me.n (car me.list)))
   (:method nullify (me) (if me.list me))
-  (:method lambda (me i) (ref me i)))
+  (:method lambda (me i) (+ me.n (ref me.list i))))
 
 (defvarl o (new (add 3 (range 10 100 10))))
 
diff --git a/txr.1 b/txr.1
index 40eea806..3251c3f6 100644
--- a/txr.1
+++ b/txr.1
@@ -25596,6 +25596,24 @@ has retrieval and storage; in that case
 .meta index
 isn't restricted to an integer value.
 
+If
+.meta seq
+is a structure, it supports
+.code ref
+if it has a
+.code lambda
+method. The
+.meta index
+argument is passed to that method, and the resulting value is
+returned. Similarly, a structure supports
+.code refset
+if it has a
+.code lambda-set
+method, which is called with
+.meta index
+and
+.metn new-value .
+
 The
 .code ref
 function retrieves an element of
-- 
cgit v1.2.3