## Copyright (C) 2007 Muthiah Annamalai <muthiah.annamalai@uta.edu>
## Copyright (C) 2012 Carnë Draug <carandraug+dev@gmail.com>
##
## 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 3 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, see <http://www.gnu.org/licenses/>.

## -*- texinfo -*-
## @deftypefn {Function File}  @var{result} = {} match ( @var{fun_handle}, @var{iterable} )
## match is filter, like Lisp's ( & numerous other language's ) function for
## Python has a built-in filter function which takes two arguments,
## a function and a list, and returns a list. 'match' performs the same
## operation like filter in Python. The match applies the
## function to each of the element in the @var{iterable} and collects
## that the result of a function applied to each of the data structure's
## elements in turn, and the return values are collected as a list of 
## input arguments, whenever the function-result is 'true' in Octave
## sense. Anything (1,true,?) evaluating to true, the argument is
## saved into the return value.
##
## @var{fun_handle} can either be a function name string or a
## function handle (recommended).
## 
## Typically you can use it as,
## @example
## match(@@(x) ( x >= 1 ), [-1 0 1 2])
##       @result{}   1   2
## @end example
## @seealso{reduce, cellfun, arrayfun, cellfun, structfun, spfun}
## @end deftypefn

function rval = match (fun_handle, data)

  if (nargin != 2)
    print_usage;
  endif

  if (isa (fun_handle, "function_handle"))
    ##do nothing
  elseif (ischar (fun_handle))
    fun_handle = str2func (fun_handle);
  else
    error ("fun_handle must either be a function handle or the name of a function");
  endif

  LD   = length(data);

  if (iscell (data))
    rval = {};
    for idx=1:LD
      if fun_handle(data{idx}), rval = [rval, data{idx}]; endif
    endfor
  elseif (ismatrix (data))
    rval = [];
    for idx=1:LD
      if fun_handle(data(idx)), rval = [rval, data(idx)]; endif
    endfor
  else
    error("data must either be a cell array or matrix");
  endif
endfunction

%!assert(match(@(x) mod(x,2),1:10),[1:2:10],0)
%!assert(match(@sin,1:10),[1:10],0)
%!assert(match(@(x) strcmp('Octave',x),{'Matlab','Octave'}),{'Octave'},0)
%!assert(match(@(x) (x>0), [-10:+10]),[1:10],0)