Mercurial > jwe > octave

changeset 20700:68e3a747ca02

Find changesets by keywords (author, files, the commit message), revision number or hash, or revset expression.
rename octave_value value extractors that accept error message args * ov.h, ov.cc (octave_value::xcell_value, octave_value::xstring_value, octave_value::xcellstr_value): Rename functions that accept error message args. Handle error directly. Only forward to functions that don't attempt type conversion. Change all uses. * ov-base.h, ov-base.cc (octave_base_value::xstring_value): Don't do type conversion. (octave_base_value::cell_value, octave_base_value::cellstr_value): Delete versions that accept error message args. * ov-str-mat.h, ov-str-mat.cc (octave_char_matrix_str::string_value, octave_char_matrix_str::cell_value): Delete.
author John W. Eaton <jwe@octave.org>
date Fri, 13 Nov 2015 14:10:26 -0500
parents e15b7963746b
children ded4efec895f
files libinterp/corefcn/__dispatch__.cc libinterp/corefcn/balance.cc libinterp/corefcn/cellfun.cc libinterp/corefcn/colloc.cc libinterp/corefcn/conv2.cc libinterp/corefcn/data.cc libinterp/corefcn/debug.cc libinterp/corefcn/dirfns.cc libinterp/corefcn/file-io.cc libinterp/corefcn/gammainc.cc libinterp/corefcn/graphics.cc libinterp/corefcn/gripes.cc libinterp/corefcn/gripes.h libinterp/corefcn/help.cc libinterp/corefcn/input.cc libinterp/corefcn/load-path.cc libinterp/corefcn/matrix_type.cc libinterp/corefcn/oct-hist.cc libinterp/corefcn/octave-link.cc libinterp/corefcn/qz.cc libinterp/corefcn/regexp.cc libinterp/corefcn/schur.cc libinterp/corefcn/spparms.cc libinterp/corefcn/strfns.cc libinterp/corefcn/symtab.cc libinterp/corefcn/syscalls.cc libinterp/corefcn/sysdep.cc libinterp/corefcn/time.cc libinterp/corefcn/toplev.cc libinterp/corefcn/urlwrite.cc libinterp/corefcn/utils.cc libinterp/corefcn/variables.cc libinterp/dldfcn/__voronoi__.cc libinterp/dldfcn/chol.cc libinterp/dldfcn/colamd.cc libinterp/dldfcn/fftw.cc libinterp/octave-value/ov-base.cc libinterp/octave-value/ov-base.h libinterp/octave-value/ov-cell.cc libinterp/octave-value/ov-cell.h libinterp/octave-value/ov-class.cc libinterp/octave-value/ov-classdef.cc libinterp/octave-value/ov-fcn-handle.cc libinterp/octave-value/ov-fcn-inline.cc libinterp/octave-value/ov-str-mat.cc libinterp/octave-value/ov-str-mat.h libinterp/octave-value/ov-struct.cc libinterp/octave-value/ov-usr-fcn.cc libinterp/octave-value/ov.cc libinterp/octave-value/ov.h libinterp/parse-tree/oct-parse.in.yy libinterp/parse-tree/pt-idx.cc
diffstat 52 files changed, 299 insertions(+), 384 deletions(-) [+]
line wrap: on
line diff
--- a/libinterp/corefcn/__dispatch__.cc	Thu Nov 12 19:27:25 2015 -0800
+++ b/libinterp/corefcn/__dispatch__.cc	Fri Nov 13 14:10:26 2015 -0500
@@ -50,13 +50,13 @@
     {
       std::string f, r, t;
 
-      f = args(0).string_value ("__dispatch__: first argument must be a function name");
+      f = args(0).xstring_value ("__dispatch__: first argument must be a function name");
 
       if (nargin > 1)
-        r = args(1).string_value ("__dispatch__: second argument must be a function name");
+        r = args(1).xstring_value ("__dispatch__: second argument must be a function name");
 
       if (nargin > 2)
-        t = args(2).string_value ("__dispatch__: third argument must be a type name");
+        t = args(2).xstring_value ("__dispatch__: third argument must be a type name");
 
       if (nargin == 1)
         {
--- a/libinterp/corefcn/balance.cc	Thu Nov 12 19:27:25 2015 -0800
+++ b/libinterp/corefcn/balance.cc	Fri Nov 13 14:10:26 2015 -0500
@@ -244,7 +244,7 @@
       if (nargin == 2)
         bal_job = "B";
       else
-        bal_job = args(2).string_value ("balance: OPT argument must be a string");
+        bal_job = args(2).xstring_value ("balance: OPT argument must be a string");
 
       if ((nn != args(1).columns ()) || (nn != args(1).rows ()))
         {
--- a/libinterp/corefcn/cellfun.cc	Thu Nov 12 19:27:25 2015 -0800
+++ b/libinterp/corefcn/cellfun.cc	Fri Nov 13 14:10:26 2015 -0500
@@ -2463,7 +2463,7 @@
 
   if (args.length () >= 1)
     {
-      const Cell x = args(0).cell_value ("cellindexmat: X must be a cell");
+      const Cell x = args(0).xcell_value ("cellindexmat: X must be a cell");
       NoAlias<Cell> y(x.dims ());
       octave_idx_type nel = x.numel ();
       octave_value_list idx = args.slice (1, args.length () - 1);
--- a/libinterp/corefcn/colloc.cc	Thu Nov 12 19:27:25 2015 -0800
+++ b/libinterp/corefcn/colloc.cc	Fri Nov 13 14:10:26 2015 -0500
@@ -80,7 +80,7 @@
 
   for (int i = 1; i < nargin; i++)
     {
-      std::string s = args(i).string_value ("colloc: expecting string argument \"left\" or \"right\"");
+      std::string s = args(i).xstring_value ("colloc: expecting string argument \"left\" or \"right\"");
 
       if ((s.length () == 1 && (s[0] == 'R' || s[0] == 'r'))
           || s == "right")
--- a/libinterp/corefcn/conv2.cc	Thu Nov 12 19:27:25 2015 -0800
+++ b/libinterp/corefcn/conv2.cc	Fri Nov 13 14:10:26 2015 -0500
@@ -329,7 +329,7 @@
       return retval;
     }
   else if (nargin == 3)
-    shape = args(2).string_value ("convn: SHAPE must be a string");
+    shape = args(2).xstring_value ("convn: SHAPE must be a string");
 
   if (shape == "full")
     ct = convn_full;
--- a/libinterp/corefcn/data.cc	Thu Nov 12 19:27:25 2015 -0800
+++ b/libinterp/corefcn/data.cc	Fri Nov 13 14:10:26 2015 -0500
@@ -6661,7 +6661,7 @@
           return retval;
         }
 
-      std::string mode = args(2).string_value ("sort: MODE must be a string");
+      std::string mode = args(2).xstring_value ("sort: MODE must be a string");
 
       if (mode == "ascend")
         smode = ASCENDING;
@@ -6940,7 +6940,7 @@
   // FIXME: shouldn't these modes be scoped inside a class?
   sortmode smode = UNSORTED;
 
-  std::string mode = arg.string_value ("issorted: expecting %s argument to be a string", argn);
+  std::string mode = arg.xstring_value ("issorted: expecting %s argument to be a string", argn);
 
   if (mode == "ascending")
     smode = ASCENDING;
@@ -6995,7 +6995,7 @@
       if (nargin == 3)
         smode = get_sort_mode_option (args(2), "third");
 
-      std::string tmp = args(1).string_value ("issorted: second argument must be a string");
+      std::string tmp = args(1).xstring_value ("issorted: second argument must be a string");
       if (tmp == "rows")
         by_rows = true;
       else
--- a/libinterp/corefcn/debug.cc	Thu Nov 12 19:27:25 2015 -0800
+++ b/libinterp/corefcn/debug.cc	Fri Nov 13 14:10:26 2015 -0500
@@ -1389,7 +1389,7 @@
         print_usage ();
       else if (nargin == 1)
         {
-          std::string arg = args(0).string_value ("dbstep: input argument must be a string");
+          std::string arg = args(0).xstring_value ("dbstep: input argument must be a string");
 
           if (arg == "in")
             {
--- a/libinterp/corefcn/dirfns.cc	Thu Nov 12 19:27:25 2015 -0800
+++ b/libinterp/corefcn/dirfns.cc	Fri Nov 13 14:10:26 2015 -0500
@@ -184,7 +184,7 @@
 
   if (args.length () == 1)
     {
-      std::string dirname = args(0).string_value ("readdir: DIR must be a string");
+      std::string dirname = args(0).xstring_value ("readdir: DIR must be a string");
 
       dir_entry dir (dirname);
 
@@ -240,13 +240,13 @@
 
   if (nargin == 2)
     {
-      std::string parent = args(0).string_value ("mkdir: PARENT must be a string");
-      std::string dir = args(1).string_value ("mkdir: DIR must be a string");
+      std::string parent = args(0).xstring_value ("mkdir: PARENT must be a string");
+      std::string dir = args(1).xstring_value ("mkdir: DIR must be a string");
 
       dirname = file_ops::concat (parent, dir);
     }
   else if (nargin == 1)
-    dirname = args(0).string_value ("mkdir: DIR must be a string");
+    dirname = args(0).xstring_value ("mkdir: DIR must be a string");
 
   if (nargin == 1 || nargin == 2)
     {
@@ -312,7 +312,7 @@
 
   if (nargin == 1 || nargin == 2)
     {
-      std::string dirname = args(0).string_value ("rmdir: DIR must be a string");
+      std::string dirname = args(0).xstring_value ("rmdir: DIR must be a string");
 
       std::string fulldir = file_ops::tilde_expand (dirname);
       int status = -1;
@@ -375,8 +375,8 @@
 
   if (args.length () == 2)
     {
-      std::string from = args(0).string_value ("link: OLD must be a string");
-      std::string to = args(1).string_value ("link: NEW must be a string");
+      std::string from = args(0).xstring_value ("link: OLD must be a string");
+      std::string to = args(1).xstring_value ("link: NEW must be a string");
 
       std::string msg;
 
@@ -412,8 +412,8 @@
 
   if (args.length () == 2)
     {
-      std::string from = args(0).string_value ("symlink: OLD must be a string");
-      std::string to = args(1).string_value ("symlink: NEW must be a string");
+      std::string from = args(0).xstring_value ("symlink: OLD must be a string");
+      std::string to = args(1).xstring_value ("symlink: NEW must be a string");
 
       std::string msg;
 
@@ -451,7 +451,7 @@
 
   if (args.length () == 1)
     {
-      std::string symlink = args(0).string_value ("readlink: SYMLINK must be a string");
+      std::string symlink = args(0).xstring_value ("readlink: SYMLINK must be a string");
 
       std::string result;
       std::string msg;
@@ -489,8 +489,8 @@
 
   if (args.length () == 2)
     {
-      std::string from = args(0).string_value ("rename: OLD must be a string");
-      std::string to = args(1).string_value ("rename: NEW must be a string");
+      std::string from = args(0).xstring_value ("rename: OLD must be a string");
+      std::string to = args(1).xstring_value ("rename: NEW must be a string");
 
       std::string msg;
 
@@ -659,7 +659,7 @@
     retval = file_ops::dir_sep_str ();
   else if (args.length () == 1)
     {
-      std::string s = args(0).string_value ("filesep: argument must be a string");
+      std::string s = args(0).xstring_value ("filesep: argument must be a string");
       if (s == "all")
         retval = file_ops::dir_sep_chars ();
       else
@@ -688,7 +688,7 @@
 
   if (nargin == 1)
     {
-      std::string sval = args(0).string_value ("pathsep: argument must be a single character");
+      std::string sval = args(0).xstring_value ("pathsep: argument must be a single character");
 
       switch (sval.length ())
         {
--- a/libinterp/corefcn/file-io.cc	Thu Nov 12 19:27:25 2015 -0800
+++ b/libinterp/corefcn/file-io.cc	Fri Nov 13 14:10:26 2015 -0500
@@ -538,9 +538,9 @@
 
   fid = -1;
 
-  std::string name = tc_name.string_value ("%s: file name must be a string", fcn);
-  std::string mode = tc_mode.string_value ("%s: file mode must be a string", fcn);
-  std::string arch = tc_arch.string_value ("%s: architecture type must be a string", fcn);
+  std::string name = tc_name.xstring_value ("%s: file name must be a string", fcn);
+  std::string mode = tc_mode.xstring_value ("%s: file mode must be a string", fcn);
+  std::string arch = tc_arch.xstring_value ("%s: architecture type must be a string", fcn);
 
   retval = do_stream_open (name, mode, arch, fid);
 
@@ -1325,7 +1325,7 @@
 
   if (! error_state)
     {
-      std::string prec = prec_arg.string_value ("fread: PRECISION must be a string");
+      std::string prec = prec_arg.xstring_value ("fread: PRECISION must be a string");
 
       int block_size = 1;
       oct_data_conv::data_type input_type;
@@ -1340,7 +1340,7 @@
 
           if (! error_state)
             {
-              std::string arch = arch_arg.string_value ("fread: ARCH architecture type must be a string");
+              std::string arch = arch_arg.xstring_value ("fread: ARCH architecture type must be a string");
 
               oct_mach_info::float_format flt_fmt
                 = oct_mach_info::string_to_float_format (arch);
@@ -1586,7 +1586,7 @@
 {
   int retval = -1;
 
-  std::string prec = prec_arg.string_value ("fwrite: PRECISION must be a string");
+  std::string prec = prec_arg.xstring_value ("fwrite: PRECISION must be a string");
 
   int block_size = 1;
   oct_data_conv::data_type output_type;
@@ -1599,7 +1599,7 @@
 
       if (! error_state)
         {
-          std::string arch = arch_arg.string_value ("fwrite: ARCH architecture type must be a string");
+          std::string arch = arch_arg.xstring_value ("fwrite: ARCH architecture type must be a string");
 
           oct_mach_info::float_format flt_fmt
             = oct_mach_info::string_to_float_format (arch);
@@ -1801,8 +1801,8 @@
 
   if (nargin == 2)
     {
-      std::string name = args(0).string_value ("popen: COMMAND must be a string");
-      std::string mode = args(1).string_value ("popen: MODE must be a string");
+      std::string name = args(0).xstring_value ("popen: COMMAND must be a string");
+      std::string mode = args(1).xstring_value ("popen: MODE must be a string");
 
       if (mode == "r")
         {
@@ -1875,12 +1875,12 @@
       std::string dir;
 
       if (len > 0)
-        dir = args(0).string_value ("tempname: DIR must be a string");
+        dir = args(0).xstring_value ("tempname: DIR must be a string");
 
       std::string pfx ("oct-");
 
       if (len > 1)
-        pfx = args(1).string_value ("tempname: PREFIX must be a string");
+        pfx = args(1).xstring_value ("tempname: PREFIX must be a string");
 
       retval = octave_tempnam (dir, pfx);
     }
@@ -2023,7 +2023,7 @@
 
   if (nargin == 1 || nargin == 2)
     {
-      std::string tmpl8 = args(0).string_value ("mkstemp: TEMPLATE argument must be a string");
+      std::string tmpl8 = args(0).xstring_value ("mkstemp: TEMPLATE argument must be a string");
 
       OCTAVE_LOCAL_BUFFER (char, tmp, tmpl8.size () + 1);
       strcpy (tmp, tmpl8.c_str ());
--- a/libinterp/corefcn/gammainc.cc	Thu Nov 12 19:27:25 2015 -0800
+++ b/libinterp/corefcn/gammainc.cc	Fri Nov 13 14:10:26 2015 -0500
@@ -85,7 +85,7 @@
 
   if (nargin == 3)
     {
-      std::string s = args(2).string_value ("gammainc: third argument must be \"lower\" or \"upper\"");
+      std::string s = args(2).xstring_value ("gammainc: third argument must be \"lower\" or \"upper\"");
 
       std::transform (s.begin (), s.end (), s.begin (), tolower);
 
--- a/libinterp/corefcn/graphics.cc	Thu Nov 12 19:27:25 2015 -0800
+++ b/libinterp/corefcn/graphics.cc	Fri Nov 13 14:10:26 2015 -0500
@@ -1673,7 +1673,7 @@
         error ("addproperty: missing possible values for radio property");
       else
         {
-          std::string sv = args(0).string_value ("addproperty: invalid argument for radio property, expected a string value");
+          std::string sv = args(0).xstring_value ("addproperty: invalid argument for radio property, expected a string value");
 
           retval = property (new radio_property (name, h, sv));
 
@@ -2151,7 +2151,7 @@
     {
       for (int i = 0; i < nargin; i += 2)
         {
-          caseless_str pname = args(i).string_value ("set: expecting argument %d to be a property name", i);
+          caseless_str pname = args(i).xstring_value ("set: expecting argument %d to be a property name", i);
 
           octave_value val = args(i+1);
 
@@ -10024,7 +10024,7 @@
 
           if (nargin > 1 && args(1).is_cellstr ())
             {
-              Array<std::string> plist = args(1).cellstr_value ("get: expecting property name or cell array of property names as second argument");
+              Array<std::string> plist = args(1).xcellstr_value ("get: expecting property name or cell array of property names as second argument");
 
               octave_idx_type plen = plist.numel ();
 
@@ -10057,7 +10057,7 @@
               caseless_str property;
 
               if (nargin > 1)
-                property = args(1).string_value ("get: expecting property name or cell array of property names as second argument");
+                property = args(1).xstring_value ("get: expecting property name or cell array of property names as second argument");
 
               vals.resize (dim_vector (len, 1));
 
@@ -10681,7 +10681,7 @@
 
           if (h.ok ())
             {
-              std::string name = args(1).string_value ("__go_execute_callback__: invalid callback name");
+              std::string name = args(1).xstring_value ("__go_execute_callback__: invalid callback name");
 
               if (nargin == 2)
                 gh_manager::execute_callback (h, name);
@@ -10855,7 +10855,7 @@
 
   if (args.length () == 1)
     {
-      std::string name = args(0).string_value ("register_graphics_toolkit: TOOLKIT must be a string");
+      std::string name = args(0).xstring_value ("register_graphics_toolkit: TOOLKIT must be a string");
 
       gtk_manager::register_toolkit (name);
     }
@@ -10969,9 +10969,9 @@
           std::string term, file, debug_file;
           bool mono;
 
-          term = args(0).string_value ("drawnow: invalid terminal TERM, expected a string value");
-
-          file = args(1).string_value ("drawnow: invalid FILE, expected a string value");
+          term = args(0).xstring_value ("drawnow: invalid terminal TERM, expected a string value");
+
+          file = args(1).xstring_value ("drawnow: invalid FILE, expected a string value");
 
           size_t pos_p = file.find_first_of ("|");
           size_t pos_c = file.find_first_not_of ("| ");
@@ -11024,7 +11024,7 @@
 
           if (! error_state)
             {
-              debug_file = (args.length () > 3 ? args(3).string_value ("drawnow: invalid DEBUG_FILE, expected a string value") : "");
+              debug_file = (args.length () > 3 ? args(3).xstring_value ("drawnow: invalid DEBUG_FILE, expected a string value") : "");
 
               graphics_handle h = gcf ();
 
@@ -11099,7 +11099,7 @@
 
       if (! error_state)
         {
-          std::string pname = args(1).string_value ("addlistener: invalid property name, expected a string value");
+          std::string pname = args(1).xstring_value ("addlistener: invalid property name, expected a string value");
 
           graphics_handle gh = gh_manager::lookup (h);
 
@@ -11166,7 +11166,7 @@
 
       if (! error_state)
         {
-          std::string pname = args(1).string_value ("dellistener: invalid property name, expected a string value");
+          std::string pname = args(1).xstring_value ("dellistener: invalid property name, expected a string value");
 
           graphics_handle gh = gh_manager::lookup (h);
 
@@ -11280,7 +11280,7 @@
 
   if (args.length () >= 3)
     {
-      std::string name = args(0).string_value ("addproperty: invalid property NAME, expected a string value");
+      std::string name = args(0).xstring_value ("addproperty: invalid property NAME, expected a string value");
 
       double h = args(1).double_value ();
 
@@ -11292,7 +11292,7 @@
             {
               graphics_object go = gh_manager::get_object (gh);
 
-              std::string type = args(2).string_value ("addproperty: invalid property TYPE, expected a string value");
+              std::string type = args(2).xstring_value ("addproperty: invalid property TYPE, expected a string value");
 
               if (! go.get_properties ().has_property (name))
                 {
--- a/libinterp/corefcn/gripes.cc	Thu Nov 12 19:27:25 2015 -0800
+++ b/libinterp/corefcn/gripes.cc	Fri Nov 13 14:10:26 2015 -0500
@@ -163,6 +163,29 @@
 }
 
 void
+gripe_wrong_type_arg (const char *s, bool is_error)
+{
+  if (is_error)
+    error ("wrong type argument '%s'", s);
+  else
+    warning ("wrong type argument '%s'", s);
+}
+
+void
+gripe_wrong_type_arg (const std::string& s, bool is_error)
+{
+  gripe_wrong_type_arg (s.c_str (), is_error);
+}
+
+void
+gripe_wrong_type_arg (const octave_value& tc, bool is_error)
+{
+  std::string type = tc.type_name ();
+
+  gripe_wrong_type_arg (type, is_error);
+}
+
+void
 gripe_wrong_type_arg_for_unary_op (const octave_value& op)
 {
   std::string type = op.type_name ();
--- a/libinterp/corefcn/gripes.h	Thu Nov 12 19:27:25 2015 -0800
+++ b/libinterp/corefcn/gripes.h	Fri Nov 13 14:10:26 2015 -0500
@@ -95,6 +95,15 @@
                       bool is_error = true);
 
 extern OCTINTERP_API void
+gripe_wrong_type_arg (const char *s, bool is_error = true);
+
+extern OCTINTERP_API void
+gripe_wrong_type_arg (const std::string& s, bool is_error = true);
+
+extern OCTINTERP_API void
+gripe_wrong_type_arg (const octave_value& tc, bool is_error = true);
+
+extern OCTINTERP_API void
 gripe_wrong_type_arg_for_unary_op (const octave_value& op);
 
 extern OCTINTERP_API void
--- a/libinterp/corefcn/help.cc	Thu Nov 12 19:27:25 2015 -0800
+++ b/libinterp/corefcn/help.cc	Fri Nov 13 14:10:26 2015 -0500
@@ -1093,7 +1093,7 @@
 
   if (args.length () == 1)
     {
-      const std::string name = args(0).string_value ("get_help_text: NAME must be a string");
+      const std::string name = args(0).xstring_value ("get_help_text: NAME must be a string");
 
       std::string text;
       std::string format;
@@ -1158,7 +1158,7 @@
 
   if (args.length () == 1)
     {
-      const std::string fname = args(0).string_value ("get_help_text_from_file: NAME must be a string");
+      const std::string fname = args(0).xstring_value ("get_help_text_from_file: NAME must be a string");
 
       std::string text;
       std::string format;
@@ -1370,7 +1370,7 @@
     retval = Cell (ffl.append (afl));
   else
     {
-      std::string dir = args(0).string_value ("__list_functions__: DIRECTORY argument must be a string");
+      std::string dir = args(0).xstring_value ("__list_functions__: DIRECTORY argument must be a string");
 
       string_vector fl = load_path::files (dir, true);
 
--- a/libinterp/corefcn/input.cc	Thu Nov 12 19:27:25 2015 -0800
+++ b/libinterp/corefcn/input.cc	Fri Nov 13 14:10:26 2015 -0500
@@ -693,7 +693,7 @@
   if (nargin == 2)
     read_as_string++;
 
-  std::string prompt = args(0).string_value ("input: unrecognized argument");
+  std::string prompt = args(0).xstring_value ("input: unrecognized argument");
 
   flush_octave_stdout ();
 
@@ -836,7 +836,7 @@
       std::string prompt;
 
       if (nargin == 1)
-        prompt = args(0).string_value ("yes_or_no: PROMPT must be a string");
+        prompt = args(0).xstring_value ("yes_or_no: PROMPT must be a string");
 
       retval = octave_yes_or_no (prompt);
     }
--- a/libinterp/corefcn/load-path.cc	Thu Nov 12 19:27:25 2015 -0800
+++ b/libinterp/corefcn/load-path.cc	Fri Nov 13 14:10:26 2015 -0500
@@ -2239,18 +2239,18 @@
 
   if (nargin == 1)
     {
-      std::string dirname = args(0).string_value ("genpath: DIR must be a string");
+      std::string dirname = args(0).xstring_value ("genpath: DIR must be a string");
 
       retval = genpath (dirname);
     }
   else if (nargin > 1)
     {
-      std::string dirname = args(0).string_value ("genpath: all arguments must be strings");
+      std::string dirname = args(0).xstring_value ("genpath: all arguments must be strings");
 
       string_vector skip (nargin - 1);
 
       for (octave_idx_type i = 1; i < nargin; i++)
-        skip[i-1] = args(i).string_value ("genpath: all arguments must be strings");
+        skip[i-1] = args(i).xstring_value ("genpath: all arguments must be strings");
 
       retval = genpath (dirname, skip);
     }
@@ -2455,7 +2455,7 @@
 
       for (int i = 0; i < nargin; i++)
         {
-          std::string arg = args(i).string_value ("addpath: all arguments must be strings");
+          std::string arg = args(i).xstring_value ("addpath: all arguments must be strings");
 
           std::list<std::string> dir_elts = split_path (arg);
 
@@ -2519,7 +2519,7 @@
 
       for (int i = 0; i < nargin; i++)
         {
-          std::string arg = args(i).string_value ("rmpath: all arguments must be strings");
+          std::string arg = args(i).xstring_value ("rmpath: all arguments must be strings");
           std::list<std::string> dir_elts = split_path (arg);
 
           for (std::list<std::string>::const_iterator p = dir_elts.begin ();
--- a/libinterp/corefcn/matrix_type.cc	Thu Nov 12 19:27:25 2015 -0800
+++ b/libinterp/corefcn/matrix_type.cc	Fri Nov 13 14:10:26 2015 -0500
@@ -215,7 +215,7 @@
             {
               // Ok, we're changing the matrix type
 
-              std::string str_typ = args(1).string_value ("matrix_type: TYPE must be a string");
+              std::string str_typ = args(1).xstring_value ("matrix_type: TYPE must be a string");
 
               // FIXME: why do I have to explicitly call the constructor?
               MatrixType mattyp = MatrixType ();
@@ -393,7 +393,7 @@
             {
               // Ok, we're changing the matrix type
 
-              std::string str_typ = args(1).string_value ("matrix_type: TYPE must be a string");
+              std::string str_typ = args(1).xstring_value ("matrix_type: TYPE must be a string");
 
               // FIXME: why do I have to explicitly call the constructor?
               MatrixType mattyp = MatrixType (MatrixType::Unknown, true);
--- a/libinterp/corefcn/oct-hist.cc	Thu Nov 12 19:27:25 2015 -0800
+++ b/libinterp/corefcn/oct-hist.cc	Fri Nov 13 14:10:26 2015 -0500
@@ -172,7 +172,7 @@
           if (i < nargin - 1)
             {
               std::string fname
-                = args(++i).string_value ("history: expecting file name for %s option",
+                = args(++i).xstring_value ("history: expecting file name for %s option",
                                           option.c_str ());
 
               command_history::set_file (fname);
--- a/libinterp/corefcn/octave-link.cc	Thu Nov 12 19:27:25 2015 -0800
+++ b/libinterp/corefcn/octave-link.cc	Fri Nov 13 14:10:26 2015 -0500
@@ -122,7 +122,7 @@
 
   if (args.length () == 1)
     {
-      std::string file = args(0).string_value ("expecting file name as argument");
+      std::string file = args(0).xstring_value ("expecting file name as argument");
 
       flush_octave_stdout ();
 
@@ -130,7 +130,7 @@
     }
   else if (args.length () == 2)
     {
-      std::string file = args(0).string_value ("expecting file name as first argument");
+      std::string file = args(0).xstring_value ("expecting file name as first argument");
 
       flush_octave_stdout ();
 
@@ -150,9 +150,9 @@
 
   if (args.length () == 3)
     {
-      std::string dlg = args(0).string_value ("invalid arguments");
-      std::string msg = args(1).string_value ("invalid arguments");
-      std::string title = args(2).string_value ("invalid arguments");
+      std::string dlg = args(0).xstring_value ("invalid arguments");
+      std::string msg = args(1).xstring_value ("invalid arguments");
+      std::string title = args(2).xstring_value ("invalid arguments");
 
       flush_octave_stdout ();
 
@@ -172,12 +172,12 @@
 
   if (args.length () == 6)
     {
-      std::string msg = args(0).string_value ("invalid arguments");
-      std::string title = args(1).string_value ("invalid arguments");
-      std::string btn1 = args(2).string_value ("invalid arguments");
-      std::string btn2 = args(3).string_value ("invalid arguments");
-      std::string btn3 = args(4).string_value ("invalid arguments");
-      std::string btndef = args(5).string_value ("invalid arguments");
+      std::string msg = args(0).xstring_value ("invalid arguments");
+      std::string title = args(1).xstring_value ("invalid arguments");
+      std::string btn1 = args(2).xstring_value ("invalid arguments");
+      std::string btn2 = args(3).xstring_value ("invalid arguments");
+      std::string btn3 = args(4).xstring_value ("invalid arguments");
+      std::string btndef = args(5).xstring_value ("invalid arguments");
 
       flush_octave_stdout ();
 
--- a/libinterp/corefcn/qz.cc	Thu Nov 12 19:27:25 2015 -0800
+++ b/libinterp/corefcn/qz.cc	Fri Nov 13 14:10:26 2015 -0500
@@ -405,7 +405,7 @@
     ord_job = 'N';
   else
     {
-      std::string tmp = args(2).string_value ("qz: OPT must be a string");
+      std::string tmp = args(2).xstring_value ("qz: OPT must be a string");
 
       if (! tmp.empty ())
         ord_job = tmp[0];
--- a/libinterp/corefcn/regexp.cc	Thu Nov 12 19:27:25 2015 -0800
+++ b/libinterp/corefcn/regexp.cc	Fri Nov 13 14:10:26 2015 -0500
@@ -288,7 +288,7 @@
     {
       std::string str;
 
-      str = args(i).string_value ("%s: optional arguments must be strings", who.c_str ());
+      str = args(i).xstring_value ("%s: optional arguments must be strings", who.c_str ());
 
       std::transform (str.begin (), str.end (), str.begin (), tolower);
 
--- a/libinterp/corefcn/schur.cc	Thu Nov 12 19:27:25 2015 -0800
+++ b/libinterp/corefcn/schur.cc	Fri Nov 13 14:10:26 2015 -0500
@@ -143,7 +143,7 @@
   std::string ord;
 
   if (nargin == 2)
-    ord = args(1).string_value ("schur: second argument must be a string");
+    ord = args(1).xstring_value ("schur: second argument must be a string");
 
   bool force_complex = false;
 
--- a/libinterp/corefcn/spparms.cc	Thu Nov 12 19:27:25 2015 -0800
+++ b/libinterp/corefcn/spparms.cc	Fri Nov 13 14:10:26 2015 -0500
@@ -167,7 +167,7 @@
     }
   else if (nargin == 2)
     {
-      std::string str = args(0).string_value ("spparms: first argument must be a string");
+      std::string str = args(0).xstring_value ("spparms: first argument must be a string");
 
       double val = args(1).double_value ();
 
--- a/libinterp/corefcn/strfns.cc	Thu Nov 12 19:27:25 2015 -0800
+++ b/libinterp/corefcn/strfns.cc	Fri Nov 13 14:10:26 2015 -0500
@@ -923,7 +923,7 @@
   std::string prefix;
 
   if (nargin > 2)
-    prefix = args(2).string_value ("list_in_columns: PREFIX must be a string");
+    prefix = args(2).xstring_value ("list_in_columns: PREFIX must be a string");
 
   std::ostringstream buf;
 
--- a/libinterp/corefcn/symtab.cc	Thu Nov 12 19:27:25 2015 -0800
+++ b/libinterp/corefcn/symtab.cc	Fri Nov 13 14:10:26 2015 -0500
@@ -1688,7 +1688,7 @@
 
   if (nargin == 1)
     {
-      std::string sval = args(0).string_value ("ignore_function_time_stamp: expecting argument to be a string");
+      std::string sval = args(0).xstring_value ("ignore_function_time_stamp: expecting argument to be a string");
 
       if (sval == "all")
         Vignore_function_time_stamp = 2;
@@ -1819,7 +1819,7 @@
 
   if (args.length () == 1)
     {
-      std::string name = args(0).string_value ("__get_cmd_line_function_text__: expecting function name");
+      std::string name = args(0).xstring_value ("__get_cmd_line_function_text__: expecting function name");
 
       octave_value ov = symbol_table::find_cmdline_function (name);
 
@@ -1852,7 +1852,7 @@
 
   if (args.length () == 2)
     {
-      std::string name = args(0).string_value ("set_variable: expecting variable name as first argument");
+      std::string name = args(0).xstring_value ("set_variable: expecting variable name as first argument");
 
       symbol_table::assign (name, args(1));
     }
@@ -1868,7 +1868,7 @@
 
   if (args.length () == 1)
     {
-      std::string name = args(0).string_value ("variable_value: expecting variable name as first argument");
+      std::string name = args(0).xstring_value ("variable_value: expecting variable name as first argument");
 
       retval = symbol_table::varval (name);
 
--- a/libinterp/corefcn/syscalls.cc	Thu Nov 12 19:27:25 2015 -0800
+++ b/libinterp/corefcn/syscalls.cc	Fri Nov 13 14:10:26 2015 -0500
@@ -189,7 +189,7 @@
 
   if (nargin == 1 || nargin == 2)
     {
-      std::string exec_file = args(0).string_value ("exec: FILE must be a string");
+      std::string exec_file = args(0).xstring_value ("exec: FILE must be a string");
 
       string_vector exec_args;
 
@@ -293,7 +293,7 @@
 
   if (nargin >= 1 && nargin <= 3)
     {
-      std::string exec_file = args(0).string_value ("popen2: COMMAND argument must be a string");
+      std::string exec_file = args(0).xstring_value ("popen2: COMMAND argument must be a string");
 
       string_vector arg_list;
 
@@ -776,7 +776,7 @@
 
   if (args.length () == 1)
     {
-      std::string fname = args(0).string_value ("lstat: NAME must be a string");
+      std::string fname = args(0).xstring_value ("lstat: NAME must be a string");
 
       file_stat fs (fname, false);
 
@@ -843,7 +843,7 @@
 
   if (nargin == 2)
     {
-      std::string name = args(0).string_value ("mkfifo: FILE must be a string");
+      std::string name = args(0).xstring_value ("mkfifo: FILE must be a string");
 
       int octal_mode = args(1).int_value ();
 
@@ -1052,7 +1052,7 @@
         }
       else
         {
-          std::string fname = args(0).string_value ("stat: NAME must be a string");
+          std::string fname = args(0).xstring_value ("stat: NAME must be a string");
 
           file_stat fs (fname);
 
@@ -1332,7 +1332,7 @@
 
   if (nargin == 1)
     {
-      std::string name = args(0).string_value ("unlink: FILE must be a string");
+      std::string name = args(0).xstring_value ("unlink: FILE must be a string");
 
       std::string msg;
 
@@ -1648,7 +1648,7 @@
 
   if (args.length () == 1)
     {
-      std::string name = args(0).string_value ("canonicalize_file_name: NAME must be a string");
+      std::string name = args(0).xstring_value ("canonicalize_file_name: NAME must be a string");
       std::string msg;
 
       std::string result = octave_canonicalize_file_name (name, msg);
--- a/libinterp/corefcn/sysdep.cc	Thu Nov 12 19:27:25 2015 -0800
+++ b/libinterp/corefcn/sysdep.cc	Fri Nov 13 14:10:26 2015 -0500
@@ -195,7 +195,7 @@
 
   if (args.length () == 1)
     {
-      std::string file = args(0).string_value ("__open_with_system_app__: argument must be a file name");
+      std::string file = args(0).xstring_value ("__open_with_system_app__: argument must be a file name");
 
 #if defined (__WIN32__) && ! defined (_POSIX_VERSION)
       HINSTANCE status = ShellExecute (0, 0, file.c_str (), 0, 0,
@@ -645,10 +645,10 @@
 
   if (nargin == 2 || nargin == 1)
     {
-      std::string var = args(0).string_value ("setenv: VAR must be a string");
+      std::string var = args(0).xstring_value ("setenv: VAR must be a string");
 
       std::string val = (nargin == 2
-                         ? args(1).string_value ("setenv: VALUE must be a string")
+                         ? args(1).xstring_value ("setenv: VALUE must be a string")
                          : std::string ());
 
       octave_env::putenv (var, val);
--- a/libinterp/corefcn/time.cc	Thu Nov 12 19:27:25 2015 -0800
+++ b/libinterp/corefcn/time.cc	Fri Nov 13 14:10:26 2015 -0500
@@ -473,7 +473,7 @@
 
   if (args.length () == 2)
     {
-      std::string fmt = args(0).string_value ("strftime: FMT must be a string");
+      std::string fmt = args(0).xstring_value ("strftime: FMT must be a string");
 
       octave_scalar_map map = args(1).scalar_map_value ();
 
@@ -524,9 +524,9 @@
 
   if (args.length () == 2)
     {
-      std::string str = args(0).string_value ("strptime: argument STR must be a string");
+      std::string str = args(0).xstring_value ("strptime: argument STR must be a string");
 
-      std::string fmt = args(1).string_value ("strptime: FMT must be a string");
+      std::string fmt = args(1).xstring_value ("strptime: FMT must be a string");
 
       octave_strptime t (str, fmt);
 
--- a/libinterp/corefcn/toplev.cc	Thu Nov 12 19:27:25 2015 -0800
+++ b/libinterp/corefcn/toplev.cc	Fri Nov 13 14:10:26 2015 -0500
@@ -1038,7 +1038,7 @@
 
       if (nargin == 3)
         {
-          std::string type_str = args(2).string_value ("system: TYPE must be a string");
+          std::string type_str = args(2).xstring_value ("system: TYPE must be a string");
 
           if (type_str == "sync")
             type = et_sync;
@@ -1068,7 +1068,7 @@
           return retval;
         }
 
-      std::string cmd_str = args(0).string_value ("system: expecting string as first argument");
+      std::string cmd_str = args(0).xstring_value ("system: expecting string as first argument");
 
 #if defined (__WIN32__) && ! defined (__CYGWIN__)
       // Work around weird double-quote handling on Windows systems.
@@ -1223,7 +1223,7 @@
 
   if (nargin == 1 || nargin == 2)
     {
-      std::string arg = args(0).string_value ("atexit: FCN argument must be a string");
+      std::string arg = args(0).xstring_value ("atexit: FCN argument must be a string");
 
       bool add_mode = true;
 
--- a/libinterp/corefcn/urlwrite.cc	Thu Nov 12 19:27:25 2015 -0800
+++ b/libinterp/corefcn/urlwrite.cc	Fri Nov 13 14:10:26 2015 -0500
@@ -345,17 +345,17 @@
       return retval;
     }
 
-  std::string url = args(0).string_value ("urlwrite: URL must be a string");
+  std::string url = args(0).xstring_value ("urlwrite: URL must be a string");
 
   // name to store the file if download is succesful
-  std::string filename = args(1).string_value ("urlwrite: LOCALFILE must be a string");
+  std::string filename = args(1).xstring_value ("urlwrite: LOCALFILE must be a string");
 
   std::string method;
   Array<std::string> param;
 
   if (nargin == 4)
     {
-      method = args(2).string_value ("urlwrite: METHOD must be a string");
+      method = args(2).xstring_value ("urlwrite: METHOD must be a string");
 
       if (method != "get" && method != "post")
         {
@@ -363,7 +363,7 @@
           return retval;
         }
 
-      param = args(3).cellstr_value ("urlwrite: parameters (PARAM) for get and post requests must be given as a cell array of strings");
+      param = args(3).xcellstr_value ("urlwrite: parameters (PARAM) for get and post requests must be given as a cell array of strings");
 
       if (param.numel () % 2 == 1)
         {
@@ -482,14 +482,14 @@
       return retval;
     }
 
-  std::string url = args(0).string_value ("urlread: URL must be a string");
+  std::string url = args(0).xstring_value ("urlread: URL must be a string");
 
   std::string method;
   Array<std::string> param;
 
   if (nargin == 3)
     {
-      method = args(1).string_value ("urlread: METHOD must be a string");
+      method = args(1).xstring_value ("urlread: METHOD must be a string");
 
       if (method != "get" && method != "post")
         {
@@ -497,7 +497,7 @@
           return retval;
         }
 
-      param = args(2).cellstr_value ("urlread: parameters (PARAM) for get and post requests must be given as a cell array of strings");
+      param = args(2).xcellstr_value ("urlread: parameters (PARAM) for get and post requests must be given as a cell array of strings");
 
       if (param.numel () % 2 == 1)
         {
@@ -552,13 +552,13 @@
     }
   else
     {
-      host = args(0).string_value ("__ftp__: HOST must be a string");
+      host = args(0).xstring_value ("__ftp__: HOST must be a string");
 
       if (nargin > 1)
-        user = args(1).string_value ("__ftp__: USER must be a string");
+        user = args(1).xstring_value ("__ftp__: USER must be a string");
 
       if (nargin > 2)
-        passwd = args(2).string_value ("__ftp__: PASSWD must be a string");
+        passwd = args(2).xstring_value ("__ftp__: PASSWD must be a string");
 
       curl_handle ch
         = ch_manager::make_curl_handle (host, user, passwd, octave_stdout);
@@ -615,7 +615,7 @@
           std::string path = "";
 
           if (nargin > 1)
-            path = args(1).string_value ("__ftp_cwd__: PATH must be a string");
+            path = args(1).xstring_value ("__ftp_cwd__: PATH must be a string");
 
           curl.cwd (path);
         }
@@ -822,7 +822,7 @@
 
       if (curl.is_valid ())
         {
-          std::string file = args(1).string_value ("__ftp_delete__: FILE must be a string");
+          std::string file = args(1).xstring_value ("__ftp_delete__: FILE must be a string");
 
           curl.del (file);
         }
@@ -851,7 +851,7 @@
 
       if (curl.is_valid ())
         {
-          std::string dir = args(1).string_value ("__ftp_rmdir__: DIR must be a string");
+          std::string dir = args(1).xstring_value ("__ftp_rmdir__: DIR must be a string");
 
           curl.rmdir (dir);
         }
@@ -880,7 +880,7 @@
 
       if (curl.is_valid ())
         {
-          std::string dir = args(1).string_value ("__ftp_mkdir__: DIR must be a string");
+          std::string dir = args(1).xstring_value ("__ftp_mkdir__: DIR must be a string");
 
           curl.mkdir (dir);
         }
@@ -909,8 +909,8 @@
 
       if (curl.is_valid ())
         {
-          std::string oldname = args(1).string_value ("__ftp_rename__: OLDNAME must be a string");
-          std::string newname = args(2).string_value ("__ftp_rename__: NEWNAME must be a string");
+          std::string oldname = args(1).xstring_value ("__ftp_rename__: OLDNAME must be a string");
+          std::string newname = args(2).xstring_value ("__ftp_rename__: NEWNAME must be a string");
 
           curl.rename (oldname, newname);
         }
@@ -939,7 +939,7 @@
 
       if (curl.is_valid ())
         {
-          std::string pat = args(1).string_value ("__ftp_mput__: PATTERN must be a string");
+          std::string pat = args(1).xstring_value ("__ftp_mput__: PATTERN must be a string");
 
           string_vector file_list;
 
@@ -1023,11 +1023,11 @@
 
       if (curl.is_valid ())
         {
-          std::string file = args(1).string_value ("__ftp_mget__: PATTERN must be a string");
+          std::string file = args(1).xstring_value ("__ftp_mget__: PATTERN must be a string");
           std::string target;
 
           if (nargin == 3)
-            target = args(2).string_value ("__ftp_mget__: TARGET must be a string") + file_ops::dir_sep_str ();
+            target = args(2).xstring_value ("__ftp_mget__: TARGET must be a string") + file_ops::dir_sep_str ();
 
           string_vector sv = curl.list ();
           octave_idx_type n = 0;
--- a/libinterp/corefcn/utils.cc	Thu Nov 12 19:27:25 2015 -0800
+++ b/libinterp/corefcn/utils.cc	Fri Nov 13 14:10:26 2015 -0500
@@ -393,7 +393,7 @@
 
   if (nargin == 2 || nargin == 3)
     {
-      std::string path = args(0).string_value ("file_in_path: PATH must be a string");
+      std::string path = args(0).xstring_value ("file_in_path: PATH must be a string");
 
       string_vector names = args(1).all_strings ();
 
@@ -756,7 +756,7 @@
 
   if (nargin == 1)
     {
-      std::string str = args(0).string_value ("do_string_escapes: STRING argument must be of type string");
+      std::string str = args(0).xstring_value ("do_string_escapes: STRING argument must be of type string");
 
       retval = do_string_escapes (str);
     }
@@ -899,7 +899,7 @@
 
   if (nargin == 1)
     {
-      std::string str = args(0).string_value ("undo_string_escapes: S argument must be a string");
+      std::string str = args(0).xstring_value ("undo_string_escapes: S argument must be a string");
 
       retval = undo_string_escapes (str);
     }
@@ -995,7 +995,7 @@
 
   if (args.length () == 1)
     {
-      std::string nm = args(0).string_value ("make_absolute_filename: FILE argument must be a file name");
+      std::string nm = args(0).xstring_value ("make_absolute_filename: FILE argument must be a file name");
 
       retval = octave_env::make_absolute (nm);
     }
@@ -1037,7 +1037,7 @@
 
   if (nargin == 1 || nargin == 2)
     {
-      dir = args(0).string_value ("dir_in_loadpath: DIR must be a directory name");
+      dir = args(0).xstring_value ("dir_in_loadpath: DIR must be a directory name");
 
       if (nargin == 1)
         retval = load_path::find_dir (dir);
--- a/libinterp/corefcn/variables.cc	Thu Nov 12 19:27:25 2015 -0800
+++ b/libinterp/corefcn/variables.cc	Fri Nov 13 14:10:26 2015 -0500
@@ -147,7 +147,7 @@
 
   if (! retval)
     {
-      std::string s = arg.string_value ("%s: expecting first argument to be a string",
+      std::string s = arg.xstring_value ("%s: expecting first argument to be a string",
                                         warn_for.c_str ());
 
       std::string cmd = header;
@@ -590,11 +590,11 @@
 
   if (nargin == 1 || nargin == 2)
     {
-      std::string name = args(0).string_value ("exist: NAME must be a string");
+      std::string name = args(0).xstring_value ("exist: NAME must be a string");
 
       if (nargin == 2)
         {
-          std::string type = args(1).string_value ("exist: TYPE must be a string");
+          std::string type = args(1).xstring_value ("exist: TYPE must be a string");
 
           if (type == "class")
             warning ("exist: \"class\" type argument is not implemented");
@@ -811,7 +811,7 @@
 
   if (nargin == 1)
     {
-      std::string sval = args(0).string_value ("%s: argument must be a single character", nm);
+      std::string sval = args(0).xstring_value ("%s: argument must be a single character", nm);
 
       switch (sval.length ())
         {
@@ -934,7 +934,7 @@
 
   if (nargin == 1)
     {
-      std::string sval = args(0).string_value ("%s: first argument must be a string", nm);
+      std::string sval = args(0).xstring_value ("%s: first argument must be a string", nm);
 
       if (empty_ok || ! sval.empty ())
         var = sval;
@@ -970,7 +970,7 @@
 
   if (nargin == 1)
     {
-      std::string sval = args(0).string_value ("%s: first argument must be a string", nm);
+      std::string sval = args(0).xstring_value ("%s: first argument must be a string", nm);
 
       int i = 0;
       for (; i < nchoices; i++)
@@ -2063,7 +2063,7 @@
 
   if (args.length () == 1)
     {
-      std::string name = args(0).string_value ("munlock: FCN must be a string");
+      std::string name = args(0).xstring_value ("munlock: FCN must be a string");
 
       munlock (name);
     }
@@ -2097,7 +2097,7 @@
 
   if (args.length () == 1)
     {
-      std::string name = args(0).string_value ("mislocked: FCN must be a string");
+      std::string name = args(0).xstring_value ("mislocked: FCN must be a string");
 
       retval = mislocked (name);
     }
@@ -2674,7 +2674,7 @@
 
   if (args.length () == 1)
     {
-      std::string name = args(0).string_value ("__varval__: expecting argument to be variable name");
+      std::string name = args(0).xstring_value ("__varval__: expecting argument to be variable name");
 
       retval = symbol_table::varval (args(0).string_value ());
     }
--- a/libinterp/dldfcn/__voronoi__.cc	Thu Nov 12 19:27:25 2015 -0800
+++ b/libinterp/dldfcn/__voronoi__.cc	Fri Nov 13 14:10:26 2015 -0500
@@ -87,7 +87,7 @@
 {
   octave_value_list retval;
 
-  std::string caller = args(0).string_value ("__voronoi__: CALLER must be a string");
+  std::string caller = args(0).xstring_value ("__voronoi__: CALLER must be a string");
 
 #if defined (HAVE_QHULL)
 
--- a/libinterp/dldfcn/chol.cc	Thu Nov 12 19:27:25 2015 -0800
+++ b/libinterp/dldfcn/chol.cc	Fri Nov 13 14:10:26 2015 -0500
@@ -162,7 +162,7 @@
   int n = 1;
   while (n < nargin)
     {
-      std::string tmp = args(n++).string_value ("chol: expecting trailing string arguments");
+      std::string tmp = args(n++).xstring_value ("chol: expecting trailing string arguments");
 
       if (tmp.compare ("vector") == 0)
         vecout = true;
--- a/libinterp/dldfcn/colamd.cc	Thu Nov 12 19:27:25 2015 -0800
+++ b/libinterp/dldfcn/colamd.cc	Fri Nov 13 14:10:26 2015 -0500
@@ -705,7 +705,7 @@
 
       if (nargin == 2)
         {
-          std::string str = args(1).string_value ("etree: TYP must be a string");
+          std::string str = args(1).xstring_value ("etree: TYP must be a string");
           if (str.find ("C") == 0 || str.find ("c") == 0)
             is_sym = false;
         }
--- a/libinterp/dldfcn/fftw.cc	Thu Nov 12 19:27:25 2015 -0800
+++ b/libinterp/dldfcn/fftw.cc	Fri Nov 13 14:10:26 2015 -0500
@@ -143,7 +143,7 @@
     }
 
 #if defined (HAVE_FFTW)
-  std::string arg0 = args(0).string_value ("fftw: first argument must be a string");
+  std::string arg0 = args(0).xstring_value ("fftw: first argument must be a string");
 
   if (arg0 == "planner")
     {
@@ -153,7 +153,7 @@
           std::transform (arg0.begin (), arg0.end (), arg0.begin (),
                           tolower);
 
-          std::string arg1 = args(1).string_value ("fftw: planner expects a string value as METHOD");
+          std::string arg1 = args(1).xstring_value ("fftw: planner expects a string value as METHOD");
 
           std::transform (arg1.begin (), arg1.end (),
                           arg1.begin (), tolower);
@@ -229,7 +229,7 @@
           std::transform (arg0.begin (), arg0.end (), arg0.begin (),
                           tolower);
 
-          std::string arg1 = args(1).string_value ("fftw: WISDOM must be a string");
+          std::string arg1 = args(1).xstring_value ("fftw: WISDOM must be a string");
 
           char *str = fftw_export_wisdom_to_string ();
 
@@ -263,7 +263,7 @@
           std::transform (arg0.begin (), arg0.end (), arg0.begin (),
                           tolower);
 
-          std::string arg1 = args(1).string_value ("fftw: WISDOM must be a string");
+          std::string arg1 = args(1).xstring_value ("fftw: WISDOM must be a string");
 
           char *str = fftwf_export_wisdom_to_string ();
 
--- a/libinterp/octave-value/ov-base.cc	Thu Nov 12 19:27:25 2015 -0800
+++ b/libinterp/octave-value/ov-base.cc	Fri Nov 13 14:10:26 2015 -0500
@@ -56,30 +56,6 @@
 #include "toplev.h"
 #include "variables.h"
 
-static void
-gripe_wrong_type_arg_with_msg (const char *name, const std::string& type,
-                               const char *fmt, va_list args)
-{
-  // Note that this method does not need to be particularly efficient
-  // since it is already an error to end up here.
-
-  // FIXME: do we want both the wrong-type-argument error and any custom
-  // error message, or just the custom error message, or should that
-  // behavior be optional in some way?
-
-  try
-    {
-      gripe_wrong_type_arg (name, type);
-    }
-  catch (const octave_execution_exception&)
-    {
-      if (fmt)
-        verror (fmt, args);
-
-      throw;
-    }
-}
-
 builtin_type_t btyp_mixed_numeric (builtin_type_t x, builtin_type_t y)
 {
   builtin_type_t retval = btyp_unknown;
@@ -561,14 +537,6 @@
   return retval;
 }
 
-Cell
-octave_base_value::cell_value (const char *fmt, va_list args) const
-{
-  gripe_wrong_type_arg_with_msg ("cell value", type_name (), fmt, args);
-
-  return Cell ();
-}
-
 Matrix
 octave_base_value::matrix_value (bool) const
 {
@@ -943,11 +911,11 @@
 }
 
 std::string
-octave_base_value::string_value (const char *fmt, va_list args) const
+octave_base_value::xstring_value (void) const
 {
-  gripe_wrong_type_arg_with_msg ("string value", type_name (), fmt, args);
-
-  return std::string ();
+  std::string retval;
+  wrong_type_arg_error ();
+  return retval;
 }
 
 Array<std::string>
@@ -959,14 +927,6 @@
   return retval;
 }
 
-Array<std::string>
-octave_base_value::cellstr_value (const char *fmt, va_list args) const
-{
-  gripe_wrong_type_arg_with_msg ("cellstr value", type_name (), fmt, args);
-
-  return Array<std::string> ();
-}
-
 Range
 octave_base_value::range_value (void) const
 {
@@ -1316,6 +1276,12 @@
      t_name.c_str (), type);
 }
 
+void
+octave_base_value::wrong_type_arg_error (void) const
+{
+  gripe_wrong_type_arg (type_name ());
+}
+
 octave_value
 octave_base_value::map (unary_mapper_t umap) const
 {
--- a/libinterp/octave-value/ov-base.h	Thu Nov 12 19:27:25 2015 -0800
+++ b/libinterp/octave-value/ov-base.h	Fri Nov 13 14:10:26 2015 -0500
@@ -481,8 +481,6 @@
 
   virtual Cell cell_value (void) const;
 
-  virtual Cell cell_value (const char *fmt, va_list args) const;
-
   virtual Matrix matrix_value (bool = false) const;
 
   virtual FloatMatrix float_matrix_value (bool = false) const;
@@ -566,13 +564,8 @@
 
   virtual std::string string_value (bool force = false) const;
 
-  virtual std::string string_value (const char *fmt, va_list args) const;
-
   virtual Array<std::string> cellstr_value (void) const;
 
-  virtual Array<std::string>
-  cellstr_value (const char *fmt, va_list args) const;
-
   virtual Range range_value (void) const;
 
   virtual octave_map map_value (void) const;
@@ -617,6 +610,11 @@
 
   virtual void convert_to_row_or_column_vector (void);
 
+  // The following extractor functions don't perform any implicit type
+  // conversions.
+
+  virtual std::string xstring_value () const;
+
   virtual bool print_as_scalar (void) const { return false; }
 
   virtual void print (std::ostream& os, bool pr_as_read_syntax = false);
@@ -832,6 +830,8 @@
 
 private:
 
+  void wrong_type_arg_error (void) const;
+
   static int curr_print_indent_level;
   static bool beginning_of_line;
 
--- a/libinterp/octave-value/ov-cell.cc	Thu Nov 12 19:27:25 2015 -0800
+++ b/libinterp/octave-value/ov-cell.cc	Fri Nov 13 14:10:26 2015 -0500
@@ -480,7 +480,10 @@
 {
   octave_value retval;
 
-  Array<std::string> tmp = cellstr_value ("sort: only cell arrays of character strings may be sorted");
+  if (! is_cellstr ())
+    error ("sort: only cell arrays of character strings may be sorted");
+
+  Array<std::string> tmp = cellstr_value ();
 
   tmp = tmp.sort (dim, mode);
 
@@ -496,7 +499,10 @@
 {
   octave_value retval;
 
-  Array<std::string> tmp = cellstr_value ("sort: only cell arrays of character strings may be sorted");
+  if (! is_cellstr ())
+    error ("sort: only cell arrays of character strings may be sorted");
+
+  Array<std::string> tmp = cellstr_value ();
 
   tmp = tmp.sort (sidx, dim, mode);
 
@@ -511,7 +517,10 @@
 {
   sortmode retval = UNSORTED;
 
-  Array<std::string> tmp = cellstr_value ("issorted: A is not a cell array of strings");
+  if (! is_cellstr ())
+    error ("issorted: A is not a cell array of strings");
+
+  Array<std::string> tmp = cellstr_value ();
 
   retval = tmp.is_sorted (mode);
 
@@ -524,7 +533,10 @@
 {
   Array<octave_idx_type> retval;
 
-  Array<std::string> tmp = cellstr_value ("sortrows: only cell arrays of character strings may be sorted");
+  if (! is_cellstr ())
+    error ("sortrows: only cell arrays of character strings may be sorted");
+
+  Array<std::string> tmp = cellstr_value ();
 
   retval = tmp.sort_rows_idx (mode);
 
@@ -536,7 +548,10 @@
 {
   sortmode retval = UNSORTED;
 
-  Array<std::string> tmp = cellstr_value ("issorted: A is not a cell array of strings");
+  if (! is_cellstr ())
+    error ("issorted: A is not a cell array of strings");
+
+  Array<std::string> tmp = cellstr_value ();
 
   retval = tmp.is_sorted_rows (mode);
 
@@ -636,49 +651,6 @@
   return retval;
 }
 
-Array<std::string>
-octave_cell::cellstr_value (const char *fmt, ...) const
-{
-  Array<std::string> retval;
-  va_list args;
-  retval = cellstr_value (fmt, args);
-  va_end (args);
-  return retval;
-}
-
-Array<std::string>
-octave_cell::cellstr_value (const char *fmt, va_list args) const
-{
-  Array<std::string> retval;
-
-  if (! fmt)
-    return cellstr_value ();
-
-  bool conversion_error = false;
-
-  if (is_cellstr ())
-    {
-      try
-        {
-          if (cellstr_cache->is_empty ())
-            *cellstr_cache = matrix.cellstr_value ();
-
-          retval = *cellstr_cache;
-        }
-      catch (const octave_execution_exception&)
-        {
-          conversion_error = true;
-        }
-    }
-  else
-    conversion_error = true;
-
-  if (conversion_error)
-    verror (fmt, args);
-
-  return retval;
-}
-
 bool
 octave_cell::print_as_scalar (void) const
 {
--- a/libinterp/octave-value/ov-cell.h	Thu Nov 12 19:27:25 2015 -0800
+++ b/libinterp/octave-value/ov-cell.h	Fri Nov 13 14:10:26 2015 -0500
@@ -135,8 +135,6 @@
 
   Cell cell_value (void) const { return matrix; }
 
-  Cell cell_value (const char *, va_list) const { return matrix; }
-
   octave_value_list list_value (void) const;
 
   octave_value convert_to_str_internal (bool pad, bool, char type) const
@@ -148,8 +146,6 @@
 
   Array<std::string> cellstr_value (const char *fmt, ...) const;
 
-  Array<std::string> cellstr_value (const char *fmt, va_list args) const;
-
   bool print_as_scalar (void) const;
 
   void print (std::ostream& os, bool pr_as_read_syntax = false);
--- a/libinterp/octave-value/ov-class.cc	Thu Nov 12 19:27:25 2015 -0800
+++ b/libinterp/octave-value/ov-class.cc	Fri Nov 13 14:10:26 2015 -0500
@@ -289,7 +289,7 @@
 
   octave_map my_map = (obvp != this) ? obvp->map_value () : map;
 
-  std::string nm = idx(0).string_value ("invalid index for class");
+  std::string nm = idx(0).xstring_value ("invalid index for class");
 
   octave_map::const_iterator p = my_map.seek (nm);
 
@@ -650,7 +650,7 @@
 
                 assert (key_idx.length () == 1);
 
-                std::string key = key_idx(0).string_value ("invalid index for class assignment");
+                std::string key = key_idx(0).xstring_value ("invalid index for class assignment");
 
                 octave_value u;
 
@@ -747,7 +747,7 @@
 
                 assert (key_idx.length () == 1);
 
-                std::string key = key_idx(0).string_value ("assignment to class element failed");
+                std::string key = key_idx(0).xstring_value ("assignment to class element failed");
 
                 map.assign (idx.front (), key, t_rhs);
 
@@ -1286,7 +1286,7 @@
                   if (! is)
                     break;
 
-                  Cell tcell = t2.is_cell () ? t2.cell_value ("load: internal error loading class elements") : Cell (t2);
+                  Cell tcell = t2.is_cell () ? t2.xcell_value ("load: internal error loading class elements") : Cell (t2);
 
                   m.assign (nm, tcell);
                 }
@@ -1423,7 +1423,7 @@
           if (! is)
             break;
 
-          Cell tcell = t2.is_cell () ? t2.cell_value ("load: internal error loading class elements") : Cell (t2);
+          Cell tcell = t2.is_cell () ? t2.xcell_value ("load: internal error loading class elements") : Cell (t2);
 
           m.assign (nm, tcell);
         }
@@ -1657,7 +1657,7 @@
     {
       octave_value t2 = dsub.tc;
 
-      Cell tcell = t2.is_cell () ? t2.cell_value ("load: internal error loading class elements") : Cell (t2);
+      Cell tcell = t2.is_cell () ? t2.xcell_value ("load: internal error loading class elements") : Cell (t2);
 
       m.assign (dsub.name, tcell);
 
@@ -1823,7 +1823,7 @@
       // Called as class constructor
       octave_function *fcn = octave_call_stack::caller ();
 
-      std::string id = args(1).string_value ("class: ID (class name) must be a string");
+      std::string id = args(1).xstring_value ("class: ID (class name) must be a string");
 
       if (fcn)
         {
@@ -1917,7 +1917,7 @@
 
   octave_value obj = args(0);  // not const because of find_parent_class ()
   std::string obj_cls = obj.class_name ();
-  Array<std::string> clsnames = args(1).cellstr_value ("isa: CLASSNAME must be a string or cell array of strings");
+  Array<std::string> clsnames = args(1).xcellstr_value ("isa: CLASSNAME must be a string or cell array of strings");
 
   boolNDArray matches (clsnames.dims (), false);
   for (octave_idx_type idx = 0; idx < clsnames.numel (); idx++)
@@ -2144,7 +2144,7 @@
 
   for (int i = 0; i < args.length (); i++)
     {
-      std::string inf_class = args(i).string_value ("superiorto: expecting argument to be class name");
+      std::string inf_class = args(i).xstring_value ("superiorto: expecting argument to be class name");
 
       // User defined classes always have higher precedence
       // than built-in classes
@@ -2185,7 +2185,7 @@
 
   for (int i = 0; i < args.length (); i++)
     {
-      std::string sup_class = args(i).string_value ("inferiorto: expecting argument to be class name");
+      std::string sup_class = args(i).xstring_value ("inferiorto: expecting argument to be class name");
 
       if (is_built_in_class (sup_class))
         {
--- a/libinterp/octave-value/ov-classdef.cc	Thu Nov 12 19:27:25 2015 -0800
+++ b/libinterp/octave-value/ov-classdef.cc	Fri Nov 13 14:10:26 2015 -0500
@@ -522,7 +522,7 @@
 
   if (args.length () == 1)
     {
-      std::string name = args(0).string_value ("fromName: invalid class name, expected a string value");
+      std::string name = args(0).xstring_value ("fromName: invalid class name, expected a string value");
 
       retval(0) = to_ov (lookup_class (name));
     }
@@ -543,7 +543,7 @@
 
       if (! error_state)
         {
-          std::string meth_name = args(1).string_value ("fevalStatic: invalid method name, expected a string value");
+          std::string meth_name = args(1).xstring_value ("fevalStatic: invalid method name, expected a string value");
 
           cdef_method meth = cls.find_method (meth_name);
 
@@ -580,7 +580,7 @@
 
       if (! error_state)
         {
-          std::string prop_name = args(1).string_value ("getConstant: invalid property name, expected a string value");
+          std::string prop_name = args(1).xstring_value ("getConstant: invalid property name, expected a string value");
 
           cdef_property prop = cls.find_property (prop_name);
 
@@ -2394,7 +2394,7 @@
 
       if (idx.front ().length () == 1)
         {
-          std::string nm = idx.front ()(0).string_value ("invalid meta.class indexing, expected a method or property name");
+          std::string nm = idx.front ()(0).xstring_value ("invalid meta.class indexing, expected a method or property name");
 
           cdef_method meth = find_method (nm);
 
@@ -3281,7 +3281,7 @@
 
   if (args.length () == 1)
     {
-      std::string name = args(0).string_value ("fromName: invalid package name, expected a string value");
+      std::string name = args(0).xstring_value ("fromName: invalid package name, expected a string value");
 
       retval(0) = to_ov (lookup_package (name));
     }
@@ -3438,7 +3438,7 @@
     case '.':
       if (idx.front ().length () == 1)
         {
-          std::string nm = idx.front ()(0).string_value ("invalid meta.package indexing, expected a symbol name");
+          std::string nm = idx.front ()(0).xstring_value ("invalid meta.package indexing, expected a symbol name");
 
 #if DEBUG_TRACE
           std::cerr << "meta.package query: " << nm << std::endl;
@@ -3823,7 +3823,7 @@
 
   if (args.length () == 1)
     {
-      std::string cname = args(0).string_value ("invalid package name, expected a string value");
+      std::string cname = args(0).xstring_value ("invalid package name, expected a string value");
 
       retval = to_ov (lookup_package (cname));
     }
@@ -3858,7 +3858,7 @@
 
   if (args.length () == 1)
     {
-      std::string cls = args(0).string_value ("invalid class name, expected a string value");
+      std::string cls = args(0).xstring_value ("invalid class name, expected a string value");
 
       retval = to_ov (lookup_class (cls));
     }
--- a/libinterp/octave-value/ov-fcn-handle.cc	Thu Nov 12 19:27:25 2015 -0800
+++ b/libinterp/octave-value/ov-fcn-handle.cc	Fri Nov 13 14:10:26 2015 -0500
@@ -1859,7 +1859,7 @@
 
   if (nargin == 1 || nargin == 2)
     {
-      std::string nm = args(0).string_value ("str2func: FCN_NAME must be a string");
+      std::string nm = args(0).xstring_value ("str2func: FCN_NAME must be a string");
 
       if (nm[0] == '@')
         {
--- a/libinterp/octave-value/ov-fcn-inline.cc	Thu Nov 12 19:27:25 2015 -0800
+++ b/libinterp/octave-value/ov-fcn-inline.cc	Fri Nov 13 14:10:26 2015 -0500
@@ -681,7 +681,7 @@
 
   if (nargin > 0)
     {
-      std::string fun = args(0).string_value ("inline: STR argument must be a string");
+      std::string fun = args(0).xstring_value ("inline: STR argument must be a string");
 
       string_vector fargs;
 
@@ -819,7 +819,7 @@
 
           for (int i = 1; i < nargin; i++)
             {
-              std::string s = args(i).string_value ("inline: expecting string arguments");
+              std::string s = args(i).xstring_value ("inline: expecting string arguments");
               fargs(i-1) = s;
             }
         }
--- a/libinterp/octave-value/ov-str-mat.cc	Thu Nov 12 19:27:25 2015 -0800
+++ b/libinterp/octave-value/ov-str-mat.cc	Fri Nov 13 14:10:26 2015 -0500
@@ -252,38 +252,6 @@
   return retval;
 }
 
-std::string
-octave_char_matrix_str::string_value (const char *fmt, va_list args) const
-{
-  std::string retval;
-
-  if (! fmt)
-    return string_value ();
-
-  bool conversion_error = false;
-
-  if (matrix.ndims () == 2)
-    {
-      charMatrix chm (matrix);
-
-      try
-        {
-          retval = chm.row_as_string (0);  // FIXME?
-        }
-      catch (const octave_execution_exception&)
-        {
-          conversion_error = true;
-        }
-    }
-  else
-    conversion_error = true;
-
-  if (conversion_error)
-    verror (fmt, args);
-
-  return retval;
-}
-
 Array<std::string>
 octave_char_matrix_str::cellstr_value (void) const
 {
@@ -303,41 +271,6 @@
   return retval;
 }
 
-Array<std::string>
-octave_char_matrix_str::cellstr_value (const char *fmt, va_list args) const
-{
-  Array<std::string> retval;
-
-  if (! fmt)
-    return cellstr_value ();
-
-  bool conversion_error = false;
-
-  if (matrix.ndims () == 2)
-    {
-      const charMatrix chm (matrix);
-      octave_idx_type nr = chm.rows ();
-      retval.clear (nr, 1);
-
-      try
-        {
-          for (octave_idx_type i = 0; i < nr; i++)
-            retval.xelem (i) = chm.row_as_string (i);
-        }
-      catch (const octave_execution_exception&)
-        {
-          conversion_error = true;
-        }
-    }
-  else
-    conversion_error = true;
-
-  if (conversion_error)
-    verror (fmt, args);
-
-  return retval;
-}
-
 void
 octave_char_matrix_str::print_raw (std::ostream& os,
                                    bool pr_as_read_syntax) const
--- a/libinterp/octave-value/ov-str-mat.h	Thu Nov 12 19:27:25 2015 -0800
+++ b/libinterp/octave-value/ov-str-mat.h	Fri Nov 13 14:10:26 2015 -0500
@@ -129,12 +129,10 @@
 
   std::string string_value (bool force = false) const;
 
-  std::string string_value (const char *fmt, va_list args) const;
+  std::string xstring_value (void) const { return string_value (); }
 
   Array<std::string> cellstr_value (void) const;
 
-  Array<std::string> cellstr_value (const char *fmt, va_list args) const;
-
   octave_value sort (octave_idx_type dim = 0, sortmode mode = ASCENDING) const
   { return octave_value (matrix.sort (dim, mode)); }
 
--- a/libinterp/octave-value/ov-struct.cc	Thu Nov 12 19:27:25 2015 -0800
+++ b/libinterp/octave-value/ov-struct.cc	Fri Nov 13 14:10:26 2015 -0500
@@ -803,7 +803,7 @@
               if (!is)
                 break;
 
-              Cell tcell = t2.is_cell () ? t2.cell_value ("load: internal error loading struct elements") : Cell (t2);
+              Cell tcell = t2.is_cell () ? t2.xcell_value ("load: internal error loading struct elements") : Cell (t2);
 
               m.setfield (nm, tcell);
             }
@@ -925,7 +925,7 @@
           if (!is)
             break;
 
-          Cell tcell = t2.is_cell () ? t2.cell_value ("load: internal error loading struct elements") : Cell (t2);
+          Cell tcell = t2.is_cell () ? t2.xcell_value ("load: internal error loading struct elements") : Cell (t2);
 
           m.setfield (nm, tcell);
         }
@@ -1022,7 +1022,7 @@
     {
       octave_value t2 = dsub.tc;
 
-      Cell tcell = t2.is_cell () ? t2.cell_value ("load: internal error loading struct elements") : Cell (t2);
+      Cell tcell = t2.is_cell () ? t2.xcell_value ("load: internal error loading struct elements") : Cell (t2);
 
       m.setfield (dsub.name, tcell);
 
@@ -1814,7 +1814,7 @@
 
       if (nargin == 2)
         {
-          Array<std::string> cstr = args(1).cellstr_value ("struct: expecting cell array of field names as second argument");
+          Array<std::string> cstr = args(1).xcellstr_value ("struct: expecting cell array of field names as second argument");
 
           retval = octave_map (args(0).dims (), cstr);
         }
--- a/libinterp/octave-value/ov-usr-fcn.cc	Thu Nov 12 19:27:25 2015 -0800
+++ b/libinterp/octave-value/ov-usr-fcn.cc	Fri Nov 13 14:10:26 2015 -0500
@@ -635,7 +635,7 @@
           octave_value varargout_varval = symbol_table::varval ("varargout");
 
           if (varargout_varval.is_defined ())
-            varargout = varargout_varval.cell_value ("expecting varargout to be a cell array object");
+            varargout = varargout_varval.xcell_value ("expecting varargout to be a cell array object");
         }
 
       retval = ret_list->convert_to_const_vector (nargout, varargout);
--- a/libinterp/octave-value/ov.cc	Thu Nov 12 19:27:25 2015 -0800
+++ b/libinterp/octave-value/ov.cc	Fri Nov 13 14:10:26 2015 -0500
@@ -1550,17 +1550,6 @@
   return rep->cell_value ();
 }
 
-Cell
-octave_value::cell_value (const char *fmt, ...) const
-{
-  Cell retval;
-  va_list args;
-  va_start (args,fmt);
-  retval = rep->cell_value (fmt, args);
-  va_end (args);
-  return retval;
-}
-
 // Define the idx_type_value function here instead of in ov.h to avoid
 // needing definitions for the SIZEOF_X macros in ov.h.
 
@@ -1895,6 +1884,42 @@
                                            type_name (), "complex vector"));
 }
 
+// NAME can't always be "x ## FCN" because some of the original
+// value extraction functions perform implicit type conversions that we
+// wish to avoid for these functions.
+
+#define XVALUE_EXTRACTOR(TYPE, NAME, FCN) \
+  TYPE \
+  octave_value::NAME (const char *fmt, ...) const \
+  { \
+    TYPE retval; \
+ \
+    try \
+      { \
+        retval = FCN (); \
+      } \
+    catch (const octave_execution_exception&) \
+      { \
+        if (fmt) \
+          { \
+            va_list args; \
+            va_start (args, fmt); \
+            verror (fmt, args); \
+            va_end (args); \
+          } \
+ \
+        throw; \
+      } \
+ \
+    return retval; \
+  }
+
+XVALUE_EXTRACTOR (Cell, xcell_value, cell_value)
+XVALUE_EXTRACTOR (std::string, xstring_value, rep->xstring_value)
+XVALUE_EXTRACTOR (Array<std::string>, xcellstr_value, cellstr_value)
+
+#undef XVALUE_EXTRACTOR
+
 octave_value
 octave_value::storable_value (void) const
 {
@@ -2845,7 +2870,7 @@
 
       for (int k = 0; k < nel; k++)
         {
-          std::string item = type(k).string_value ("%s: type(%d) must be a string", name, k+1);
+          std::string item = type(k).xstring_value ("%s: type(%d) must be a string", name, k+1);
 
           if (item == "{}")
             type_string[k] = '{';
--- a/libinterp/octave-value/ov.h	Thu Nov 12 19:27:25 2015 -0800
+++ b/libinterp/octave-value/ov.h	Fri Nov 13 14:10:26 2015 -0500
@@ -770,8 +770,6 @@
 
   Cell cell_value (void) const;
 
-  Cell cell_value (const char *fmt, ...) const;
-
   Matrix matrix_value (bool frc_str_conv = false) const
   { return rep->matrix_value (frc_str_conv); }
 
@@ -899,29 +897,9 @@
   std::string string_value (bool force = false) const
   { return rep->string_value (force); }
 
-  std::string string_value (const char *fmt, ...) const
-  {
-    std::string retval;
-    va_list args;
-    va_start (args,fmt);
-    retval = rep->string_value (fmt, args);
-    va_end (args);
-    return retval;
-  }
-
   Array<std::string> cellstr_value (void) const
   { return rep->cellstr_value (); }
 
-  Array<std::string> cellstr_value (const char *fmt, ...) const
-  {
-    Array<std::string> retval;
-    va_list args;
-    va_start (args,fmt);
-    retval = rep->cellstr_value (fmt, args);
-    va_end (args);
-    return retval;
-  }
-
   Range range_value (void) const
   { return rep->range_value (); }
 
@@ -1016,6 +994,21 @@
   float_complex_vector_value (bool frc_str_conv = false,
                               bool frc_vec_conv = false) const;
 
+  // Extract values of specific types without any implicit type
+  // conversions.  Throw an error if an object is the wrong type for
+  // the requested value extraction.
+  //
+  // These functions are intended to provide a simple way to extract
+  // values of specific types and display error messages that are more
+  // meaningful than the generic "error: wrong type argument 'cell'"
+  // message.
+
+  Cell xcell_value (const char *fmt, ...) const;
+
+  std::string xstring_value (const char *fmt, ...) const;
+
+  Array<std::string> xcellstr_value (const char *fmt, ...) const;
+
   // Possibly economize a lazy-indexed value.
 
   void maybe_economize (void)
--- a/libinterp/parse-tree/oct-parse.in.yy	Thu Nov 12 19:27:25 2015 -0800
+++ b/libinterp/parse-tree/oct-parse.in.yy	Fri Nov 13 14:10:26 2015 -0500
@@ -4548,7 +4548,7 @@
   std::string arg;
 
   if (nargin == 1)
-    arg = args(0).string_value ("mfilename: expecting argument to be a character string");
+    arg = args(0).xstring_value ("mfilename: expecting argument to be a character string");
 
   std::string fname;
 
@@ -4599,12 +4599,12 @@
 
   if (nargin == 1 || nargin == 2)
     {
-      std::string file_name = args(0).string_value ("source: expecting file name as argument");
+      std::string file_name = args(0).xstring_value ("source: expecting file name as argument");
 
       std::string context;
 
       if (nargin == 2)
-        context = args(1).string_value ("source: expecting context to be character string");
+        context = args(1).xstring_value ("source: expecting context to be character string");
 
       source_file (file_name, context);
     }
@@ -4785,7 +4785,7 @@
 
   if (nargin > 0)
     {
-      const std::string name (args(0).string_value ("builtin: function name (F) must be a string"));
+      const std::string name (args(0).xstring_value ("builtin: function name (F) must be a string"));
 
       octave_value fcn = symbol_table::builtin_find (name);
 
@@ -4885,7 +4885,7 @@
 eval_string (const octave_value& arg, bool silent, int& parse_status,
              int nargout)
 {
-  std::string s = arg.string_value ("eval: expecting std::string argument");
+  std::string s = arg.xstring_value ("eval: expecting std::string argument");
 
   return eval_string (s, silent, parse_status, nargout);
 }
@@ -5051,7 +5051,7 @@
 
   if (nargin == 3)
     {
-      std::string context = args(0).string_value ("assignin: CONTEXT must be a string");
+      std::string context = args(0).xstring_value ("assignin: CONTEXT must be a string");
 
       unwind_protect frame;
 
@@ -5064,7 +5064,7 @@
 
       frame.add_fcn (octave_call_stack::pop);
 
-      std::string nm = args(1).string_value ("assignin: VARNAME must be a string");
+      std::string nm = args(1).xstring_value ("assignin: VARNAME must be a string");
 
       if (valid_identifier (nm))
         symbol_table::assign (nm, args(2));
@@ -5092,7 +5092,7 @@
 
   if (nargin > 1)
     {
-      std::string context = args(0).string_value ("evalin: CONTEXT must be a string");
+      std::string context = args(0).xstring_value ("evalin: CONTEXT must be a string");
 
       unwind_protect frame;
 
@@ -5192,7 +5192,7 @@
 
   if (nargin == 1 || nargin == 2)
     {
-      std::string file = args(0).string_value ("__parse_file__: expecting file name as argument");
+      std::string file = args(0).xstring_value ("__parse_file__: expecting file name as argument");
 
       std::string full_file = octave_env::make_absolute (file);
 
--- a/libinterp/parse-tree/pt-idx.cc	Thu Nov 12 19:27:25 2015 -0800
+++ b/libinterp/parse-tree/pt-idx.cc	Fri Nov 13 14:10:26 2015 -0500
@@ -209,7 +209,7 @@
         {
           octave_value t = df->rvalue1 ();
 
-          fn = t.string_value ("dynamic structure field names must be strings");
+          fn = t.xstring_value ("dynamic structure field names must be strings");
         }
       else
         panic_impossible ();