--- a/src/oct-map.cc
+++ b/src/oct-map.cc
@@ -42,6 +42,14 @@
     (*rep)[fields(i)] = i;
 }
 
+octave_fields::octave_fields (const char * const *fields)
+  : rep (new fields_rep)
+{
+  octave_idx_type n = 0;
+  while (*fields)
+    (*rep)[std::string (*fields++)] = n++;
+}
+
 bool
 octave_fields::isfield (const std::string& field) const
 {
@@ -112,8 +120,6 @@
 {
   bool retval = true;
 
-  octave_idx_type n = nfields ();
-
   iterator p = begin (), q = other.begin ();
   for (; p != end () && q != other.end (); p++, q++)
     {
@@ -135,8 +141,6 @@
 octave_fields::equal_up_to_order (const octave_fields& other,
                                   Array<octave_idx_type>& perm) const
 {
-  bool retval = true;
-
   octave_idx_type n = nfields ();
   if (perm.length () != n)
     perm.clear (1, n);

--- a/src/oct-map.h
+++ b/src/oct-map.h
@@ -58,6 +58,7 @@
 
   octave_fields (void) : rep (&nil_rep) { rep->count++; }
   octave_fields (const string_vector&);
+  octave_fields (const char * const *);
 
   ~octave_fields (void)
     {
@@ -145,11 +146,11 @@
 class OCTINTERP_API
 octave_scalar_map
 {
+public:
+
   octave_scalar_map (const octave_fields& k)
     : xkeys (k), xvals (k.nfields ()) { }
 
-public:
-
   octave_scalar_map (void) : xkeys (), xvals () { }
 
   octave_scalar_map (const string_vector& k)
@@ -253,14 +254,14 @@
 class OCTINTERP_API
 octave_map
 {
+public:
+
   octave_map (const octave_fields& k)
     : xkeys (k), xvals (k.nfields ()), dimensions () { }
 
   octave_map (const dim_vector& dv, const octave_fields& k)
     : xkeys (k), xvals (k.nfields (), Cell (dv)), dimensions (dv) { }
 
-public:
-
   typedef octave_scalar_map element_type;
 
   octave_map (void) : xkeys (), xvals (), dimensions () { }