# [texhax] Puzzling (La)TeX output

Barbara Beeton bnb at ams.org
Thu May 4 23:52:31 CEST 2006

    I tripped over this and can't explain it; I hope someone here will
show me what I am missing:

Using this source:

=====
\newcommand{\dx}{\rm dx}

$\Phi(\dx_i)=dx_i$.
=====

the braces get stripped off the expansion of the
command, so the \rm isn't scoped.  you could change
this to

\newcommand{\dx}{{\rm dx}}

but it would be better to use the latex2e method of
indicating font changes in math by this:

\newcommand{\dx}{\mathrm{dx}}

that definitively limits the scope of the roman to
its argument {dx} .
-- bb