`\rm` control sequence undefined in custom class but works for `report`, how to find the problem

Question

I am using custom class and when I use ${\rm test}$ I get complaint that it is Undefined control sequence. It does not in text mode either. I tried searching through the cls file and other relevant linked files for \rm but I can never find where it would be removed, actaully, it is used in the class as:

\newcommand\@makecopyrightpage{
   \ColumnSave
   \pagenumbering{roman}
   \setcounter{page}{2}
   %\thispagestyle{empty} 
   \thispagestyle{plain}
   \null
   \vfill
   \if@copyright
      \begin{center}
         %\normalsize \rm Copyright \copyright\ \@copyrightyear
         %\ifx\@copyrightyear\@degreeyear\else , \@degreeyear \fi
         %\ by \@author \\
         %\@copyrightinfo
         \normalsize \normalfont \copyright\  \@copyrightyear  \hspace{1pt}
         \@author \\
      \end{center}
   \fi
   \vfill
   \ColumnRestore
}

the only other places that \rm can be found in the class:

\def\ps@headings{\def\@oddfoot{}\def\@evenfoot{}%     No feet.
\def\@oddhead{\hbox {}\slshape \rightmark \hfil \rm\thepage}% Heading.
\def\chaptermark##1{\markright {\uppercase{\ifnum \c@secnumdepth >\m@ne
  \@chapapp\ \thechapter. \ \fi ##1}}}}

% Definition of 'myheadings' page style.
%
\def\ps@myheadings{\def\@oddhead{\hbox{}\slshape\rightmark \hfil \rm\thepage}%
\def\@oddfoot{}\def\@evenhead{\rm \thepage\hfil\slshape\leftmark\hbox {}}%
\def\@evenfoot{}\def\sectionmark##1{}\def\subsectionmark##1{}}

When i switch to \documentclass{report} everything works. How can i investigate where it got lost?

\rm has been deprecated and not defined by default in latex since latex2e was released in 1993. report class defines it for compatibility with documents written in the 1980s but other classes may not. — David Carlisle, Mar 03 '20 at 20:35
The \rm command has been deprecated for 25 years. Some document classes define it for back compatibility. There are classes and packages around that use \rm and siblings: it's a sure sign that they should be avoided. — egreg, Mar 03 '20 at 20:36
@DavidCarlisle So it has to be explicitly defined in the class for it to work, thus if I find it definition in the report class and copy it over, it should do the trick? — atapaka, Mar 03 '20 at 20:37
use \rmfamily or if you really must, copy the definition of \rm from report, which is \DeclareOldFontCommand{\rm}{\normalfont\rmfamily}{\mathrm} — David Carlisle, Mar 03 '20 at 20:37
Does the postings Why \rm in math mode works in some tex editors and not in others? and Is there any reason not to use \let to redefine a deprecated control sequence to the currently recommended one? answer your query? — Mico, Mar 03 '20 at 20:38
@DavidCarlisle I read in Lamport's book that \rmfamily does not work in math mode (which is the whole purpose for me to need \rm). So what is there in math mode? Also, if it is undefined in the class, how can the class use it in the above code? — atapaka, Mar 03 '20 at 20:39
\mathrm{zzz} in math mode but none of the uses you show in your question are in math. — David Carlisle, Mar 03 '20 at 20:40
@leosenko - Lamport's book deals with LateX2.09, i.e., the version of LaTeX available up until 1993. As David Carlisle wrote in an earlier comment, LaTeX2e has been around since 1994. — Mico, Mar 03 '20 at 20:41
That is the definition of \rm copied from report, it says to use \normalfont\rmfamily in text and \mathrm in math. — David Carlisle, Mar 03 '20 at 20:41
@Mico er no, not unless you have a very old 1980s copy of Lamport. Lamport's book is still the official documentation for 2e. — David Carlisle, Mar 03 '20 at 20:42
@Mico if there is a other good book, i am all ears but sincerely, getting any good information on TeX function declaration and how they work is really a pain... I have found Lamport's book to be the best so far covering Latex as well as some Tex commands. — atapaka, Mar 03 '20 at 20:43
texdoc clsguide is the document that comes with latex that describes how to write a class and also how to define \rm if you really must. See section 6.4 — David Carlisle, Mar 03 '20 at 20:47
@DavidCarlisle - I guess I'm guilty of having "a very old 1980s copy" of Lamport's book... — Mico, Mar 03 '20 at 21:05
See What are good learning resources for a LaTeX beginner? . Of the books shown there, Kopka & Daly remains my perennial favorite. Not only a good resource for the beginner, it remains useful as a highly functional reference, with good examples and clear explanations. — barbara beeton, Mar 03 '20 at 21:29

score 5 · Accepted Answer · answered Mar 03 '20 at 21:05

The syntax for roman in math in LaTeX is $\mathrm{test}$ not ${\rm test}$ .

\rm has not been defined in LaTeX since LaTeX2e was released in 1993.

As described in clsguide the guide to writing latex classes that comes with latex, you could define \rm via

\DeclareOldFontCommand{\rm}{\normalfont\rmfamily}{\mathrm}

and the report class does this, however that was over compatibility concerns with documents written in the 1980s. No documents written this century should be using \rm so for a class being written now it is better not to define \rm and assume that the document has correct markup. That way bad markup in the document is easily found and corrected.

`\rm` control sequence undefined in custom class but works for `report`, how to find the problem

1 Answers1