--- /dev/null
+## Copyright (C) 2008-2012 Bill Denney, Robert Platt
+##
+## This file is part of Octave.
+##
+## Octave 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 3 of the License, or (at
+## your option) any later version.
+##
+## Octave 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 Octave; see the file COPYING. If not, see
+## <http://www.gnu.org/licenses/>.
+
+## -*- texinfo -*-
+## @deftypefn {Function File} {@var{varname} =} genvarname (@var{str})
+## @deftypefnx {Function File} {@var{varname} =} genvarname (@var{str}, @var{exclusions})
+## Create unique variable(s) from @var{str}. If @var{exclusions} is
+## given, then the variable(s) will be unique to each other and to
+## @var{exclusions} (@var{exclusions} may be either a string or a cellstr).
+##
+## If @var{str} is a cellstr, then a unique variable is created for each
+## cell in @var{str}.
+##
+## @example
+## @group
+## x = 3.141;
+## genvarname ("x", who ())
+## @result{} x1
+## @end group
+## @end example
+##
+## If @var{wanted} is a cell array, genvarname will make sure the returned
+## strings are distinct:
+##
+## @example
+## @group
+## genvarname (@{"foo", "foo"@})
+## @result{}
+## @{
+## [1,1] = foo
+## [1,2] = foo1
+## @}
+## @end group
+## @end example
+##
+## Note that the result is a char array/cell array of strings, not the
+## variables themselves. To define a variable, @code{eval()} can be
+## used. The following trivial example sets @code{x} to @code{42}.
+##
+## @example
+## @group
+## name = genvarname ("x");
+## eval ([name " = 42"]);
+## @result{} x = 42
+## @end group
+## @end example
+##
+## Also, this can be useful for creating unique struct field names.
+##
+## @example
+## @group
+## x = struct ();
+## for i = 1:3
+## x.(genvarname ("a", fieldnames (x))) = i;
+## endfor
+## @result{} x =
+## @{
+## a = 1
+## a1 = 2
+## a2 = 3
+## @}
+## @end group
+## @end example
+##
+## Since variable names may only contain letters, digits and underscores,
+## genvarname replaces any sequence of disallowed characters with
+## an underscore. Also, variables may not begin with a digit; in this
+## case an underscore is added before the variable name.
+##
+## Variable names beginning and ending with two underscores "__" are valid but
+## they are used internally by octave and should generally be avoided, therefore
+## genvarname will not generate such names.
+##
+## genvarname will also make sure that returned names do not clash with
+## keywords such as "for" and "if". A number will be appended if necessary.
+## Note, however, that this does @strong{not} include function names,
+## such as "sin". Such names should be included in @var{avoid} if necessary.
+## @seealso{isvarname, exist, tmpnam, eval}
+## @end deftypefn
+
+## Authors: Rob Platt <robert.platt@postgrad.manchester.ac.uk>
+## Bill Denney <bill@denney.ws>
+
+function varname = genvarname (str, exclusions)
+
+ strinput = ischar (str);
+ ## Process the inputs
+ if (nargin < 2)
+ exclusions = {};
+ elseif (ischar (exclusions))
+ if (rows (exclusions) != 1)
+ error ("genvarname: if more than one exclusion is given, it must be a cellstr");
+ endif
+ exclusions = {exclusions};
+ elseif (! iscellstr (exclusions))
+ error ("genvarname: EXCLUSIONS must be a string or a cellstr");
+ endif
+ if (ischar (str))
+ if (rows (str) != 1)
+ error ("genvarname: if more than one STR is given, it must be a cellstr");
+ endif
+ str = {str};
+ elseif (! iscellstr (str))
+ error ("genvarname: STR must be a string or a cellstr");
+ endif
+
+ validchars = cstrcat ("A":"Z", "a":"z", "0":"9", "_");
+
+ varname = cell (size (str));
+ for i = 1:numel (str)
+ ## Perform any modifications to the varname to make sure that it is
+ ## a valid variable name.
+
+ ## remove invalid characters
+ str{i}(! ismember (str{i}, validchars)) = "_";
+ ## do not use keywords
+ if (iskeyword (str{i}))
+ str{i} = cstrcat ("_", str{i});
+ endif
+ ## double underscores at the beginning and end are reserved variables
+ underscores = (str{i} == "_");
+ if (any (underscores))
+ firstnon = find (!underscores, 1);
+ lastnon = find (!underscores, 1, "last");
+ str{i}([1:firstnon-2, lastnon+2:end]) = [];
+ endif
+ ## The variable cannot be empty
+ if (isempty (str{i}))
+ str{i} = "x";
+ endif
+ ## it cannot start with a number
+ if (ismember (str{i}(1), "0":"9"))
+ str{i} = cstrcat ("_", str{i});
+ endif
+
+ ## make sure that the variable is unique relative to other variables
+ ## and the exclusions list
+ excluded = any (strcmp (str{i}, exclusions));
+ if (excluded && ismember (str{i}(end), "0":"9"))
+ ## if it is not unique and ends with a digit, add an underscore to
+ ## make the variable name more readable ("x1_1" instead of "x11")
+ str{i}(end+1) = "_";
+ endif
+ varname(i) = str(i);
+ idx = 0;
+ while excluded
+ idx++;
+ varname{i} = sprintf("%s%d", str{i}, idx);
+ excluded = any (strcmp (varname{i}, exclusions));
+ endwhile
+ exclusions(end+1) = varname(i);
+ endfor
+
+ if strinput
+ varname = varname{1};
+ endif
+
+endfunction
+
+## Tests
+## a single argument
+%!assert(genvarname("a"), "a")
+## a single argument with a non-conflicting exception
+%!assert(genvarname("a", "b"), "a")
+## a single argument with a conflicting exception
+%!assert(genvarname("a", "a"), "a1")
+## a single argument as a cell
+%!assert(genvarname({"a"}), {"a"})
+%!assert(genvarname({"a"}, "b"), {"a"})
+%!assert(genvarname({"a"}, {"b"}), {"a"})
+%!assert(genvarname({"a"}, "a"), {"a1"})
+%!assert(genvarname({"a"}, {"a"}), {"a1"})
+## Test different arguments
+## orientation
+%!assert(genvarname({"a" "b"}), {"a" "b"})
+%!assert(genvarname({"a";"b"}), {"a";"b"})
+%!assert(genvarname({"a" "a"}), {"a" "a1"})
+%!assert(genvarname({"a" "b";"c" "d"}), {"a" "b";"c" "d"})
+%!assert(genvarname({"a" "a" "a";"a" "a" "a"}), {"a" "a2" "a4";"a1" "a3" "a5"})
+## more than one repetition
+%!assert(genvarname({"a" "a" "a"}), {"a" "a1" "a2"})
+%!assert(genvarname({"a" "a" "a"}, {"a" "a1" "a2"}), {"a3" "a4" "a5"})
+## more than one repetition not in order
+%!assert(genvarname({"a" "b" "a" "b" "a"}), {"a" "b" "a1" "b1" "a2"})
+## Variable name munging
+%!assert (genvarname ("__x__"), "_x_")
+%!assert (genvarname ("123456789"), "_123456789")
+%!assert (genvarname ("_$1__"), "_1_")
+%!assert (genvarname ("__foo__", "_foo_"), "_foo_1")
+%!assert (genvarname ("1million_and1", "_1million_and1"), "_1million_and1_1")
+%!assert (genvarname ({"", "", ""}), {"x", "x1", "x2"})
+%!assert (genvarname ("if"), "_if")
+%!assert (genvarname ({"if", "if", "if"}), {"_if", "_if1", "_if2"})