function point_num = product_rule_size ( list_filename, list_num )

%% PRODUCT_RULE_SIZE returns the size of a product rule of distinct factors.
%
%  Licensing:
%
%    This code is distributed under the GNU LGPL license. 
%
%  Modified:
%
%    10 May 2007
%
%  Author:
%
%    John Burkardt
%
%  Parameters:
%
%    Input, string LIST_FILENAME, a file containing a list
%    of prefixes defining quadrature rules.
%
%    Input, integer LIST_NUM, the number of prefixes in the file.
%
%    Output, integer POINT_NUM, the number of points in the product rule.
%
  point_num = 1;

  list_unit = fopen ( list_filename, 'rt' );

  if ( list_unit < 0 )
    fprintf ( 1, '\n' );
    fprintf ( 1, 'PRODUCT_RULE_SIZE - Fatal error!\n' );
    fprintf ( 1, '  Nonzero value of IOS while opening list file.\n' );
    error ( 'PRODUCT_RULE_SIZE - Fatal error!' );
  end

  for list = 1 : list_num

    quad_1d_filename = fgetl ( list_unit );

    quad_x_1d_filename = strcat ( quad_1d_filename, '_x.txt' );

    [ dim_num_1d, point_num_1d ] = dtable_header_read ( quad_x_1d_filename );

    point_num = point_num * point_num_1d;

  end

  fclose ( list_unit );