doc: Use more coding conventions in Object Oriented reference example code. * examples/code/@FIRfilter/FIRfilter.m, examples/code/@FIRfilter/FIRfilter_aggregation.m, examples/code/@FIRfilter/subsasgn.m, examples/code/@FIRfilter/subsref.m, examples/code/@polynomial/display.m, examples/code/@polynomial/double.m, examples/code/@polynomial/get.m, examples/code/@polynomial/mtimes.m, examples/code/@polynomial/numel.m, examples/code/@polynomial/polynomial.m, examples/code/@polynomial/polynomial_superiorto.m, examples/code/@polynomial/polyval.m, examples/code/@polynomial/roots.m, examples/code/@polynomial/set.m, examples/code/@polynomial/subsasgn.m, examples/code/@polynomial/subsref.m: Remove "Function File" from deftypefn. Use names of variables in error messages. Surround invalid items in error messages with single quotes. Use meaningful variable names.

function val = get (p, prop)

  if (nargin < 1 || nargin > 2)
    print_usage ();
  endif

  if (nargin == 1)
    val.poly = p.poly;
  else
    if (! ischar (prop))
      error ("@polynomial/get: PROPERTY must be a string");
    endif

    switch (prop)
      case "poly"
        val = p.poly;
      otherwise
        error ("@polynomial/get: invalid PROPERTY '%s'", prop);
    endswitch
  endif

endfunction