# HG changeset patch
# User John W. Eaton <address@hidden>
# Date 1566417718 14400
#      Wed Aug 21 16:01:58 2019 -0400
# Node ID ff8d4dddc5e9b8fa1a7ef4c8f8392c8e80971677
# Parent  a24338d5a788e1e23a42714c6a8208b646e2530b
improve convert_to_const_vector

diff --git a/libinterp/octave-value/ovl.cc b/libinterp/octave-value/ovl.cc
--- a/libinterp/octave-value/ovl.cc
+++ b/libinterp/octave-value/ovl.cc
@@ -31,6 +31,19 @@ along with Octave; see the file COPYING.
 // We are likely to have a lot of octave_value_list objects to allocate,
 // so make the grow_size large.
 
+octave_value_list::octave_value_list (const std::list<octave_value>& lst)
+{
+  size_t nel = lst.size ();
+
+  if (nel > 0)
+    {
+      m_data.resize (nel);
+      octave_idx_type k = 0;
+      for (const auto& ov : lst)
+        m_data[k++] = ov;
+    }
+}
+
 octave_value_list::octave_value_list (const std::list<octave_value_list>& lst)
 {
   octave_idx_type n = 0;
diff --git a/libinterp/octave-value/ovl.h b/libinterp/octave-value/ovl.h
--- a/libinterp/octave-value/ovl.h
+++ b/libinterp/octave-value/ovl.h
@@ -78,7 +78,8 @@ public:
   octave_value_list (octave_value_list&& obj)
     : m_data (std::move (obj.m_data)), m_names (std::move (obj.m_names)) { }
 
-  // Concatenation constructor.
+  // Concatenation constructors.
+  octave_value_list (const std::list<octave_value>&);
   octave_value_list (const std::list<octave_value_list>&);
 
   ~octave_value_list (void) = default;
diff --git a/libinterp/parse-tree/pt-eval.cc b/libinterp/parse-tree/pt-eval.cc
--- a/libinterp/parse-tree/pt-eval.cc
+++ b/libinterp/parse-tree/pt-eval.cc
@@ -1796,7 +1796,7 @@ namespace octave
 
     int len = arg_list->length ();
 
-    std::list<octave_value_list> args;
+    std::list<octave_value> args;
 
     auto p = arg_list->begin ();
     for (int k = 0; k < len; k++)
@@ -1817,18 +1817,20 @@ namespace octave
             octave_value tmp = evaluate (elt);
 
             if (tmp.is_cs_list ())
-              args.push_back (tmp.list_value ());
+              {
+                octave_value_list tmp_ovl = tmp.list_value ();
+
+                for (octave_idx_type i = 0; i < tmp_ovl.length (); i++)
+                  args.push_back (tmp_ovl(i));
+              }
             else if (tmp.is_defined ())
               args.push_back (tmp);
           }
         else
-          {
-            args.push_back (octave_value ());
-            break;
-          }
+          break;
       }
 
-    return args;
+    return octave_value_list (args);
   }
 
   octave_value_list