## Copyright (C) 2012 Pantxo Diribarne
##
## 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 Octave; see the file COPYING.  If not, see
## <http://www.gnu.org/licenses/>.

## Private internal function to check if a argument is a transformation
## structure (as created by maketform and to be use by findbounds,
## imtransform, and the like)

## Author: Pantxo Diribarne <pantxo@dibona>

function out = istform (T)
  out = true;
  if (!isstruct (T))
    out = false;
  else
    required = {"ndims_in";"ndims_out"; ...
                "forward_fcn"; "inverse_fcn"; ...
                "tdata"};

    fields = fieldnames (T);
    tst = cellfun (@(x) any (strcmp (fields, x)), required);
    if (! all (tst))
      out = false
    endif
  endif 
endfunction