[texhax] macro expansion trouble

[Neal H. Walfield]

At Sat, 4 Aug 2012 16:09:31 +0200,
Neal H. Walfield wrote:
> The following is a minimal working example:

Here is an even more minimal example (no need for \input):

  \documentclass{article}
  \usepackage{pgfplots} 

  \begin{document}

  \def\Arg{width=0.5\textwidth}
  \begin{tikzpicture}
  \begin{axis}[\Arg]
    \addplot[only marks, mark=o] coordinates {
      (3.000000, 1469.000000)
       (4.000000, 461.000000)
    };
  \end{axis}
  \end{tikzpicture}

  \end{document}

Note: I only get the error if \Arg includes a control sequence.
Doing:

  \def\Arg{width=5in}

works and does not generate an error.

Neal