## Copyright (C) 2004, 2005, 2006, 2007, 2008 David Bateman & Andy Adler
##
## 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{y} =} spfun (@var{f},@var{x})
## Compute @code{f(@var{x})} for the non-zero values of @var{x}.
## This results in a sparse matrix with the same structure as 
## @var{x}. The function @var{f} can be passed as a string, a
## function handle or an inline function.
## @end deftypefn

function t = spfun (f, s)

  if (nargin != 2)
    print_usage ();
  endif

  [i, j, v] = find (s);
  [m, n] = size (s);

  if (isa (f, "function_handle") || isa (f, "inline function"))
    t = sparse (i, j, f(v), m, n);
  else
    t = sparse(i, j, feval (f, v), m, n);
  endif

endfunction

%!assert(spfun('exp',[1,2;3,0]),sparse([exp(1),exp(2);exp(3),0]))
%!assert(spfun('exp',sparse([1,2;3,0])),sparse([exp(1),exp(2);exp(3),0]))
%!assert(spfun(@exp,[1,2;3,0]),sparse([exp(1),exp(2);exp(3),0]))
%!assert(spfun(@exp,sparse([1,2;3,0])),sparse([exp(1),exp(2);exp(3),0]))