From 286bb507a316acefcecc87865f3a152c403ea8b3 Mon Sep 17 00:00:00 2001
From: Kaz Kylheku <kaz@kylheku.com>
Date: Tue, 1 Sep 2020 06:40:36 -0700
Subject: New function: reject.

* eval.c (eva_init): Register reject intrinsic.

* lib.c (appendl): New static function.
(reject): New function.

* lib.h (reject): Declared.

* txr.1: Documented.
---
 txr.1 | 70 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 70 insertions(+)

(limited to 'txr.1')

diff --git a/txr.1 b/txr.1
index 84d2512f..a44fb8c5 100644
--- a/txr.1
+++ b/txr.1
@@ -31826,6 +31826,76 @@ from the input sequence, and a new
 is returned whose storage is initialized by converting the extracted
 values back to the foreign representation.
 
+.coNP Function @ reject
+.synb
+.mets (reject < sequence >> { index-list | << function })
+.syne
+.desc
+The
+.code reject
+function returns a sequence, of the same kind as
+.metn sequence ,
+which consists of all those elements of
+.meta sequence
+which are not identified by the indices in
+.metn index-list ,
+which may be a list or a vector.
+
+If
+.meta function
+is given instead of
+.metn index-list ,
+then
+.meta function
+is invoked with
+.meta sequence
+as its argument. The return value is then taken as
+if it were the
+.meta index-list
+argument .
+
+If
+.code sequence
+is a hash, then
+.meta index-list
+represents a list of keys. The
+.code reject
+function returns a duplicate of the hash, in which
+the keys specified in
+.meta index-list
+do not appear.
+
+Otherwise if
+.meta sequence
+is a vector-like sequence, then the behavior of
+.code reject
+may be understood by the following equivalence:
+
+.verb
+  (reject seq idx)  -->  (make-like
+                           [apply append (split* seq idx)]
+                           seq)
+.brev
+
+where it is to be understood that
+.meta seq
+is evaluated only once.
+
+If
+.meta sequence
+is a list, then, similarly, the following equivalence applies:
+
+.verb
+  (reject seq idx)  -->  (make-like
+                           [apply append* (split* seq idx)]
+                           seq)
+.brev
+
+The input sequence is split into pieces at the indicated indices, such that
+the elements at the indices are removed and do not appear in the pieces. The
+pieces are then appended together in order, and the resulting list is coerced
+into the same type of sequence as the input sequence.
+
 .coNP Function @ relate
 .synb
 .mets (relate < domain-seq < range-seq <> [ default-val ])
-- 
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