Dithering with Symbols not working

[seebs]

Hello,
I am attempting to reproduce the "Dithering with Symbols" example here:
http://www.imagemagick.org/Usage/quantize/#diy_symbols
However I receive the error:
"unable to parse expression 'u[floor(15.9999*u)+1]' @error/fx.c/FxGetSymbol/1842."

Is anyone else able to reproduce this error? Any clues how to fix or is this a bug?

ImageMagick 6.8.6-0 2013-05-15
Windows 7 64-bit

[snibgo]

The script as given is for Unix. For Windows, you'll need certain changes. In this case, probably use double quotes (") instead of single quotes ('). See http://www.imagemagick.org/Usage/windows/

[seebs]

Ah, yes that was the issue.
Replacing them with double-quotes solves the problem. Thank you for your assistance.