The polynom
style (version “2006/04/20 0.17 (CH,HA)” from texlive 2012) has to be told about which tokens represent variables. The manual has an example like this:
\polyset{vars=XYZ\xi, % make X, Y, Z, and \xi into variables
delims={[}{]}}% nongrowing brackets
When I try to typeset this in a minimal document
\documentclass{article}
\usepackage{polynom,amsmath,amssymb}
\begin{document}
\polyset{vars=XYZ\xi,delims={[}{]}}
\polylongdiv{\xi^2-1}{\xi-1}
\end{document}
I get the following error message:
! Missing \endcsname inserted.
<to be read again>
\xi
l.4 \polyset{vars=XYZ\xi,delims={[}{]}}
So there appears to be a problem trating greek letters as variable tokens. Can anyone suggest a way to resolve this, i.e. to actually typeset a ξ or similar greek letter as a variable in a polynom long division?
Best Answer
The manual seems wrong about this: you must use simple letters for your polynomials; but you can use a devious hack:
Just choose an unused letter for your Greek one, et voilà.
A bit of explanation is in order. When TeX is in math mode, it looks at letters (more precisely, character tokens of category 11 or 12) as math characters, which have a mathcode attached to them. Control sequences can denote a mathcode and this is the case for the Greek letters: the definition one finds in
fontmath.ltx
ultimately boils down to the primitive statement
where the first digit
0
tells TeX\xi
is an ordinary symbol; the second digit is the "math group" (1 corresponds toletters
); the third and fourth digits tell the slot in the font where the symbol should be taken from.With
we assign
A
a mathcode with the same specifications; actually we don't need to know what mathcode is associated to\xi
, because any control sequence defined with\mathchardef
can be used as a number when the syntax of TeX requires one. So withwe're saying that any
A
in a math formula, from that point on, will just behave like\xi
. Of course this respect grouping, so all of this takes place in a group; I delimited it with\begingroup
and\endgroup
,{
and}
would be good too, but the former delimiters pose less problems than the latter in certain situations.