--- a/src/mappers.h
+++ b/src/mappers.h
@@ -47,19 +47,18 @@
 {
   builtin_mapper_function (ch_Mapper ch = 0, d_d_Mapper dd = 0,
 			   d_c_Mapper dc = 0, c_c_Mapper cc = 0,
-			   double l = 0.0, double u = 0.0, int cfr = 0,
+			   double l = 0.0, double u = 0.0, int f = 0,
 			   const string n = string (),
 			   const string& h = string ())
     : ch_mapper (ch), d_d_mapper (dd), d_c_mapper (dc), c_c_mapper (cc),
-      lower_limit (l), upper_limit (u), can_return_complex_for_real_arg (cfr),
+      lower_limit (l), upper_limit (u), flag (f),
       name (n), help_string (h) { }
 
   builtin_mapper_function (const builtin_mapper_function& mf)
     : ch_mapper (mf.ch_mapper), d_d_mapper (mf.d_d_mapper),
       d_c_mapper (mf.d_c_mapper), c_c_mapper (mf.c_c_mapper),
       lower_limit (mf.lower_limit), upper_limit (mf.upper_limit),
-      can_return_complex_for_real_arg (mf.can_return_complex_for_real_arg),
-      name (mf.name), help_string (mf.help_string) { }
+      flag (mf.flag), name (mf.name), help_string (mf.help_string) { }
 
   builtin_mapper_function& operator = (const builtin_mapper_function& mf)
     {
@@ -71,7 +70,7 @@
 	  c_c_mapper = mf.c_c_mapper;
 	  lower_limit = mf.lower_limit;
 	  upper_limit = mf.upper_limit;
-	  can_return_complex_for_real_arg = mf.can_return_complex_for_real_arg;
+	  flag = mf.flag;
 	  name = mf.name;
 	  help_string = mf.help_string;
 	}
@@ -86,7 +85,17 @@
   c_c_Mapper c_c_mapper;
   double lower_limit;
   double upper_limit;
-  int can_return_complex_for_real_arg;
+
+  // For ch_mapper:
+  //
+  //   0  =>  this function returns a matrix of ones and zeros
+  //   1  =>  this function returns a numeric matrix (any values)
+  //   2  =>  this function returns a string array
+  //
+  // For other mappers, nonzero means that this function can return a
+  // complex value for some real arguments.
+  int flag;
+
   string name;
   string help_string;
 };