## Copyright (C) 2007, 2008, 2009 David Bateman
## Copyright (C) 2010 VZLU Prague
##
## 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} {} structfun (@var{func}, @var{S})
## @deftypefnx {Function File} {[@var{a}, @dots{}] =} structfun (@dots{})
## @deftypefnx {Function File} {} structfun (@dots{}, "ErrorHandler", @var{errfunc})
## @deftypefnx {Function File} {} structfun (@dots{}, "UniformOutput", @var{val})
## 
## Evaluate the function named @var{name} on the fields of the structure
## @var{S}.  The fields of @var{S} are passed to the function @var{func}
## individually.
##
## @code{structfun} accepts an arbitrary function @var{func} in the form of 
## an inline function, function handle, or the name of a function (in a 
## character string).  In the case of a character string argument, the 
## function must accept a single argument named @var{x}, and it must return 
## a string value.  If the function returns more than one argument, they are
## returned as separate output variables.
##
## If the parameter "UniformOutput" is set to true (the default), then the
## function
## must return a single element which will be concatenated into the
## return value.  If "UniformOutput" is false, the outputs are placed into a
## structure
## with the same fieldnames as the input structure.
## 
## @example
## @group
## s.name1 = "John Smith"; 
## s.name2 = "Jill Jones"; 
## structfun (@@(x) regexp (x, '(\w+)$', "matches")@{1@}, s, 
##            "UniformOutput", false)
##     @result{}
##    @{
##      name1 = Smith
##      name2 = Jones
##    @} 
## @end group
## @end example
## 
## Given the parameter "ErrorHandler", @var{errfunc} defines a function to
## call in case @var{func} generates an error.  The form of the function is
## 
## @example
## function [@dots{}] = errfunc (@var{se}, @dots{})
## @end example
## 
## @noindent
## where there is an additional input argument to @var{errfunc} relative to
## @var{func}, given by @var{se}.  This is a structure with the elements
## "identifier", "message" and "index", giving respectively the error
## identifier, the error message, and the index into the input arguments
## of the element that caused the error.  For an example on how to use
## an error handler, @pxref{doc-cellfun, @code{cellfun}}. 
##
## @seealso{cellfun, arrayfun, spfun}
## @end deftypefn

function varargout = structfun (func, S, varargin);

  if (nargin < 2)
    print_usage ();
  endif

  nargs = length (varargin);

  recognized_opts = {"UniformOutput", "ErrorHandler"};
  uo_str = recognized_opts{1};

  uniform_output = true;

  while (nargs >= 2)
    opt_match = strcmpi (varargin{nargs-1}, recognized_opts);
    if (opt_match(1))
      uniform_output = varargin{nargs};
    endif
    if (any (opt_match))
      nargs -= 2;
    else
      break;
    endif
  endwhile

  if (nargs > 0)
    error ("structfun: invalid options");
  endif

  varargout = cell (max ([nargout, 1]), 1);
  [varargout{:}] = cellfun (func, struct2cell (S), varargin{:});

  if (! uniform_output)
    varargout = cellfun (@cell2struct, varargout, {fieldnames(S)}, {1}, uo_str, false);
  endif
endfunction


%!test
%! s.name1 = "John Smith"; 
%! s.name2 = "Jill Jones"; 
%! l.name1 = "Smith";
%! l.name2 = "Jones";
%! o = structfun (@(x) regexp (x, '(\w+)$', "matches"){1}, s, 
%!                "UniformOutput", false);
%! assert (o, l);

%!function [a, b] = twoouts (x)
%! a = x + x;
%! b = x * x;

%!test
%! s = struct ("a", {1, 2, 3}, "b", {4, 5, 6});
%! c(1:2, 1, 1) = [2; 8];
%! c(1:2, 1, 2) = [4; 10];
%! c(1:2, 1, 3) = [6; 12];
%! d(1:2, 1, 1) = [1; 16];
%! d(1:2, 1, 2) = [4; 25];
%! d(1:2, 1, 3) = [9; 36];
%! [aa, bb] = structfun(@twoouts, s);
%! assert(aa, c);
%! assert(bb, d);

%!test
%! s = struct ("a", {1, 2, 3}, "b", {4, 5, 6});
%! c = struct ("a", {2, 4, 6}, "b", {8, 10, 12});
%! d = struct ("a", {1, 4, 9}, "b", {16, 25, 36});
%! [aa, bb] = structfun(@twoouts, s, "UniformOutput", false);
%! assert(aa, c);
%! assert(bb, d);
