Adding revappend and nreconc.

* eval.c (eval_init): Register revappend and nreconc
intrinsics.

* lib.c (list_collect_nreconc): New function.
(revlist): New static function.
(list_collect_revappend): New function.
(revappend, nreconc): New functions.

* lib.h (revappend, nreconc): Declared.
(list_collect_nreconc, list_collect_revappend): Declared.

* txr.1: Documented revappend and nreconc.

1 files changed, 27 insertions, 0 deletions

diff --git a/txr.1 b/txr.1
index aa22c111..f56cccb2 100644
--- a/txr.1
+++ b/txr.1
@@ -14447,6 +14447,33 @@ traverse the last argument.)
   (append '(a . b) 3 '(1 2 3)) -> **error**
 .cble
 
+.coNP Functions @ revappend and @ nreconc
+.synb
+.mets (revappend < list1 << list2 )
+.mets (nreconc < list1 << list2 )
+.syne
+.desc
+The
+.code revappend
+function returns a list consisting of
+.code list2
+appended to a reversed copy of
+.metn list1 .
+The returned object shares structure
+with
+.metn list2 ,
+which is unmodified.
+
+The
+.code nreconc
+function behaves similarly, except
+that the the returned object may share
+structure with not only
+.meta list2
+but also
+.metn list1 ,
+which is modified.
+
 .coNP Function @ list
 .synb
 .mets (list << value *)