From b8b1c891f17d26cf3b13e77c1657cd855ae6543b Mon Sep 17 00:00:00 2001
From: Kaz Kylheku <kaz@kylheku.com>
Date: Sun, 11 Jan 2015 09:34:29 -0800
Subject: * eval.c (merge_wrap): Make generic over sequences.

* txr.1: Update documentation for merge function.
---
 ChangeLog |  6 ++++++
 eval.c    | 23 ++++++++++++++++++-----
 txr.1     | 21 +++++++++++----------
 3 files changed, 35 insertions(+), 15 deletions(-)

diff --git a/ChangeLog b/ChangeLog
index 0747d675..52c8a16f 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,9 @@
+2015-01-11  Kaz Kylheku  <kaz@kylheku.com>
+
+	* eval.c (merge_wrap): Make generic over sequences.
+
+	* txr.1: Update documentation for merge function.
+
 2015-01-05  Kaz Kylheku  <kaz@kylheku.com>
 
 	* match.c (h_trailer): Bugfix: not returning new variable
diff --git a/eval.c b/eval.c
index 71f2470e..b02e4d0b 100644
--- a/eval.c
+++ b/eval.c
@@ -3399,12 +3399,25 @@ static val pprinl(val obj, val stream)
   return ret;
 }
 
-static val merge_wrap(val list1, val list2, val lessfun, val keyfun)
-{
-  keyfun = default_arg(keyfun, identity_f);
-  lessfun = default_arg(lessfun, less_f);
+static val merge_wrap(val seq1, val seq2, val lessfun, val keyfun)
+{
+  if (!nullify(seq1)) {
+    if (type(seq1) == type(seq2))
+      return seq2;
+    return make_like(tolist(seq2), seq1);
+  } else if (!nullify(seq2)) {
+    if (type(seq1) == type(seq2))
+      return seq1;
+    return make_like(tolist(seq1), seq1);
+  } else {
+    val list1 = tolist(seq1);
+    val list2 = tolist(seq2);
 
-  return merge(list1, list2, lessfun, keyfun);
+    keyfun = default_arg(keyfun, identity_f);
+    lessfun = default_arg(lessfun, less_f);
+
+    return make_like(merge(list1, list2, lessfun, keyfun), seq1);
+  }
 }
 
 void eval_init(void)
diff --git a/txr.1 b/txr.1
index 5f886a8d..8b329d7b 100644
--- a/txr.1
+++ b/txr.1
@@ -14786,26 +14786,27 @@ value.
 .SS* List Sorting
 .coNP Function @ merge
 .synb
-.mets (merge < list1 < list2 >> [ lessfun <> [ keyfun ]])
+.mets (merge < seq1 < seq2  >> [ lessfun <> [ keyfun ]])
 .syne
 .desc
 The
 .code merge
-function merges two sorted lists
-.meta list1
+function merges two sorted sequences
+.meta seq1
 and
-.meta list2
+.meta seq2
 into a single
-sorted list. The semantics and defaulting behavior of the
+sorted sequence. The semantics and defaulting behavior of the
 .meta lessfun
 and
 .meta keyfun
-arguments are the same as those of the sort function. The input lists
-are assumed to be sorted according to these functions.
+arguments are the same as those of the sort function.
+
+The sequence which is returned is of the same kind as
+.metn seq1 .
 
-This function is destructive. The application should not retain references to
-the input lists, since the output list is formed out of the structure of the
-input lists.
+This function is destructive of any inputs that are lists. If the output
+is a list, it is formed out of the structure of the input lists.
 
 .coNP Function @ multi-sort
 .synb
-- 
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