Replace cellfun() occurrences with faster code where possible. * scripts/help/doc_cache_create.m: Use built-in "isclass" rather than ischar. Use addpath and rmpath with multiple inputs rather than cellfun. * scripts/image/imformats.m: Use isfield with cell string list rather than cellfun. * scripts/image/private/__imread__.m: Use ismember to replace cellfun/strcmpi combo. * scripts/miscellaneous/what.m: Re-order if/elseif tree. * scripts/pkg/private/rebuild.m: Replace cellfun with strcat call. * scripts/plot/axis.m: Use comma-separated lists to replace cellfun. * scripts/plot/pareto.m: Use cellstr on char array to replace cellfun. * scripts/plot/private/__gnuplot_print__.m: Use @times, rather than anonymous function, in cellfun call. * scripts/plot/private/__line__.m: White space cleanup. * scripts/plot/private/__patch__.m: Use ismember to replace cellfun/strcmpi combo. Use in-place '|=' operator for performance. * scripts/plot/struct2hdl.m: Use ismember to replace cellfun/strcmp combo. * scripts/polynomial/splinefit.m: Use built-in "isclass" rather than ischar. * scripts/special-matrix/gallery.m: Remove anonymous functions inside cellfuns. * scripts/strings/strsplit.m: Correct comment character to '#' from '%'. * scripts/strings/untabify.m: Use multiple argument form of cellfun to get rid of anonymous function. * scripts/testfun/__run_test_suite__.m: Remove anonymous function from within cellfun. * scripts/ui/inputdlg.m: Use built-in "isclass" rather than ischar.

## Copyright (C) 1998-2012 John W. Eaton
##
## 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} {} isletter (@var{s})
## Return a logical array which is true where the elements of @var{s}
## are letters and false where they are not.  This is an alias for
## the @code{isalpha} function.
## @seealso{isalpha, isdigit, ispunct, isspace, iscntrl, isalnum}
## @end deftypefn

## Author: jwe

function retval = isletter (s)

  if (nargin != 1)
    print_usage ();
  endif

  retval = isalpha (s);

endfunction


%!error isletter ()
%!error isletter ("a", "b")