--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/main/strings/str_incr.m	Wed Dec 05 05:40:31 2001 +0000
@@ -0,0 +1,57 @@
+## Copyright (C) 2001 Albert Danial
+##
+## This program is free software; you can redistribute it and/or modify
+## it under the terms of the GNU General Public License as published by
+## the Free Software Foundation; either version 2 of the License, or
+## (at your option) any later version.
+##
+## This program is distributed in the hope that it will be useful,
+## but WITHOUT ANY WARRANTY; without even the implied warranty of
+## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+## GNU General Public License for more details.
+##
+## You should have received a copy of the GNU General Public License
+## along with this program; if not, write to the Free Software
+## Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
+
+function [new_name] = str_incr(old_name, nLetters);
+    # [new_name] = str_incr(old_name, nLetters);
+    #
+    #  Increments by one letter the substring comprising the first nLetters
+    #  of old_name.  The first nLetters may contain only characters in
+    #  'a'.. 'z'.
+    #  
+    #  Examples:  str_incr("aa",   2) returns "ab"  
+    #             str_incr("ab",   2) returns "ac"  
+    #             str_incr("az",   2) returns "ba"  
+    #             str_incr("zz",   2) returns an overflow error
+    #             str_incr("abcd", 2) returns "accd"  
+
+    letters = toascii(old_name);
+    if (nLetters > size(old_name, 2))
+        error("str_incr:  2nd argument too large\n");
+    endif
+
+    for i = nLetters:-1:1
+
+        # make sure the letter is in range
+        if ( (letters(i) < toascii("a")) || (letters(i) > toascii("z")) )
+            err_msg = sprintf(
+            "str_incr: character %d not in 'a'..'z'\n", i);
+            error(err_msg);
+        endif
+
+        if (letters(i) < toascii("z"))
+            ++letters(i);
+            break;
+        elseif (i == 1)  # bummer, ran out of characters
+            error("str_incr:  name length overflow\n");
+        else
+            letters(i) = toascii("a");
+        endif
+
+    endfor
+
+    new_name = setstr(letters);
+    return
+endfunction