From 25e2779a39949a11ac597774aa4207d4d04a54d3 Mon Sep 17 00:00:00 2001
From: Kaz Kylheku <kaz@kylheku.com>
Date: Sun, 28 Jun 2020 11:47:13 -0700
Subject: New function: maprodo.

maprodo is like maprod, but doesn't collect or return
anything. It's the Cartesian product analog of mapdo.

* eval.c (collect_nothing, maprodo): New static functions.
(eval_init): Register maprodo intrinsic.

* txr.1: Documented.
---
 eval.c | 12 ++++++++++++
 txr.1  | 28 +++++++++++++++++++++-------
 2 files changed, 33 insertions(+), 7 deletions(-)

diff --git a/eval.c b/eval.c
index cd282da0..1d1b6cf0 100644
--- a/eval.c
+++ b/eval.c
@@ -5463,6 +5463,17 @@ val maprendv(val fun, struct args *lists)
   return prod_common(fun, lists, list_collect_append, mappendv);
 }
 
+static loc collect_nothing(loc ptail, val obj)
+{
+  (void) obj;
+  return ptail;
+}
+
+static val maprodo(val fun, struct args *lists)
+{
+  return prod_common(fun, lists, collect_nothing, mappendv);
+}
+
 static val symbol_value(val sym)
 {
   uses_or2;
@@ -6535,6 +6546,7 @@ void eval_init(void)
   reg_fun(intern(lit("mapdo"), user_package), func_n1v(mapdov));
   reg_fun(intern(lit("maprod"), user_package), func_n1v(maprodv));
   reg_fun(intern(lit("maprend"), user_package), func_n1v(maprendv));
+  reg_fun(intern(lit("maprodo"), user_package), func_n1v(maprodo));
   reg_fun(intern(lit("window-map"), user_package), func_n4(window_map));
   reg_fun(intern(lit("window-mappend"), user_package), func_n4(window_mappend));
   reg_fun(intern(lit("window-mapdo"), user_package), func_n4(window_mapdo));
diff --git a/txr.1 b/txr.1
index 64d5a691..5a5c0017 100644
--- a/txr.1
+++ b/txr.1
@@ -32131,25 +32131,28 @@ and so doesn't return.
   -> (2 4)
 .brev
 
-.coNP Functions @ maprod and @ maprend
+.coNP Functions @, maprod @ maprend and @ maprodo
 .synb
 .mets (maprod < function << iterable *)
 .mets (maprend < function << iterable *)
+.mets (maprodo < function << iterable *)
 .syne
 .desc
 The
-.code maprod
-and
+.codn maprod ,
 .code maprend
+and
+.code maprodo
 functions resemble
-.code mapcar
+.codn mapcar ,
+.code mappend
 and
-.codn mappend ,
+.codn mapdo ,
 respectively. When given no
 .meta iterable
 arguments or exactly one
 .meta iterable
-argument, they behave exactly like those two functions.
+argument, they behave exactly like those three functions.
 
 When two or more
 .meta iterable
@@ -32157,7 +32160,9 @@ arguments are present,
 .code maprod
 differs from
 .code mapcar
-in the following way. Whereas
+in the following way, as do the remaining functions
+from their aforementioned counterparts.
+Whereas
 .code mapcar
 iterates over the
 .meta iterable
@@ -32216,6 +32221,15 @@ and the final result is converted to the same kind of sequence as the leftmost
 .meta iterable
 if possible.
 
+The
+.code maprodo
+function, like
+.codn mapdo ,
+ignores the result of
+.meta function
+and returns
+.codn nil .
+
 The combination iteration gives priority to the rightmost
 .metn iterable ,
 which means that the rightmost element of each generated tuple varies
-- 
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