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

[Joel C. Salomon]

Ross Moore wrote:
>> I’d read about that trick.  The problem is that it want to treat $x'$
>> like $x^\prime$ using the large CM Math prime character.
> 
> 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.

I look a look at the character set specimen for Cambria Math at
<http://www.tiro.nu/Articles/Cambria/Cambria_Math_Basic_Spec_V1.pdf>,
and near the bottom of Page 2 are what seem to be the large prime
characters.

I have no idea how to get at these glyphs—they do not seem to be in
Unicode or in the font’s PUA—but if they can be used they might make a
more natural match to TeX’s primes behavior.

—Joel Salomon