breqn

ody in the frame and from then on treat the body as a single box instead of
multiple line boxes. But I had a notion that it might be possible some day to
support vertical stretching of the frame.
16 Prelim
This package doesn’t work with L ATEX 2.09, nor with other versions of L ATEX earlier
than 1994/12/01.
1 〈∗package〉
2 \NeedsTeXFormat{LaTeX2e}
Declare package name and date.
3 \RequirePackage{expl3}[2009/08/05]
4 \ProvidesExplPackage{breqn}{2012/05/10}{0.98b}{Breaking equations}
Regrettably, breqn is internally a mess, so we have to take some odd steps.
5 \ExplSyntaxOff
17 Package options
Most options are set with the \options command (which calls \setkeys) because
the standard package option mechanism doesn’t provide support for key-value
syntax.
First we need to get the catcodes sorted out.
6 \edef\breqnpopcats{%
7 \catcode\number‘\"=\number\catcode‘\"
8 \relax}
9 \AtEndOfPackage{\breqnpopcats}%
10 \catcode‘\^=7 \catcode‘\_=8 \catcode‘\"=12 \relax
11 \DeclareOption{mathstyleoff}{%
12 \PassOptionsToPackage{mathstyleoff}{flexisym}%
13 }
Process options.
14 \ProcessOptions\relax
18 Required packages
The flexisym package makes it possible to attach extra actions to math symbols,
in particular mathbin, mathrel, mathopen, and mathclose symbols. Normally it
would suffice to call \RequirePackage without any extra testing, but the nature of
the package is such that it is likely to be called earlier with different (no) options.
Then is it really helpful to be always warning the user about ‘Incompatible Package
Options!’? I don’t think so.
15 \@ifpackageloaded{flexisym}{}{%
16 \RequirePackage{flexisym}[2009/08/07]
16