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.

1 files changed, 18 insertions, 0 deletions

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