[XeTeX] Using the Unicode prime character (Was re. Single glyphs from a font)

[Joel C. Salomon]

Ross Moore wrote:
> There is a discussion of these "pseudo-script" characters also
> taking place on a MathML-related list.
>
> Some software uses the Unicode character directly, while
> other software (such as TeX) has a character that is required
> to be superscripted; e.g., as $...^\prime ...$.
> With these it is not normal to use the oversized character by itself.
> It is only included in the font for the convenience of encoding,
> and when it might be needed at \Large (etc.) sizes.

Can you point me to that discussion?

>> The Unicode prime character is already at the correct size and position.
>> Try $\prime{}'$ and you’ll see that the second one is shifted up by some
>> amount.  (With $\prime'$ it’s even worse.)
>
> I don't see a difference in the placement. (see attached image)

Here’s my code; picture is attached.

\documentclass{minimal}
\usepackage{fontspec, xunicode, xltxtra,unicode-math}

\setmainfont[Mapping=tex-text]{Cambria}
\setmathfont{Cambria Math}

\makeatletter
    \let\UnicodeMathSymbol\um at mathsymbol@noparse
    \UnicodeMathSymbol{"02032}{\prime}{\mathord}{prime}%
    \let\prime ′
\makeatother

\begin{document}
    $x'\prime$, $x\prime'$, $x\prime{}'$
\end{document}

—Joel Salomon
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