# Using bm with eulervm gives inconsistent ‘<’ and ‘>’ characters

I prefer to use bm package to bold math. However, I noticed that when used with eulervm, this gives inconsistent results for ‘<’ and ‘>’ characters.

I wonder what causes it and can the usage bm be fixed to get proper ‘<’.

\documentclass{article}

\usepackage[utf8]{inputenc}
\usepackage[T1]{fontenc}

%\usepackage{amsmath}

\usepackage[euler-digits,euler-hat-accent]{eulervm}

\usepackage{bm}

\begin{document}

\texttt{\hphantom{mathbold}\llap{bm}}: \quad $1 + 1 < 3; \quad \bm{1 + 1 < 3}$

\texttt{mathbold}: \quad $1 + 1 < 3; \quad \mathbold{1 + 1 < 3}$

\end{document}

There is an inconsistency in the shape of < and > in the zeurm10 and zeurb10 fonts used for the symbols with eulervm active:

\documentclass{article}

\usepackage{amsmath}
\usepackage[euler-digits,euler-hat-accent]{eulervm}
\usepackage{bm}

\begin{document}

\begin{tabular}{@{}ll@{}}
bm: & $1 + 1 < 3$; $\bm{1 + 1 < 3}$ \\
mathbold: & $1 + 1 < 3$; $\mathbold{1 + 1 < 3}$
\end{tabular}

{\usefont{U}{zeur}{m}{n}\symbol{"3C}}

{\usefont{U}{zeur}{b}{n}\symbol{"3C}}

\end{document}

With \mathbold, which is a math alphabet selection, only letters and numbers become bold, but not other symbols.

You can work around the inconsistency by using Computer Modern for the < and > symbols.

\documentclass{article}

\usepackage{amsmath}
\usepackage[euler-digits,euler-hat-accent]{eulervm}
\usepackage{bm}

\DeclareSymbolFont{cmletters}{OML}{cmm}{m}{it}
\SetSymbolFont{cmletters}{bold}{OML}{cmm}{b}{it}
\DeclareMathSymbol{<}{\mathrel}{cmletters}{"3C}
\DeclareMathSymbol{>}{\mathrel}{cmletters}{"3E}

\begin{document}

\begin{tabular}{@{}ll@{}}
bm: & $1 + 1 < 3$; $\bm{1 + 1 < 3}$ \\
mathbold: & $1 + 1 < 3$; $\mathbold{1 + 1 < 3}$
\end{tabular}

\end{document}

• the important point being: It's not my fault – David Carlisle Dec 22 '18 at 18:22
• please take a closer look -- the result in the last example still isn't the same with \bm and \mathbold. – barbara beeton Dec 23 '18 at 1:41
• @barbarabeeton Of course they aren't the same: \mathbold is a math alphabet switch, which doesn't act on symbols such as <. – egreg Dec 23 '18 at 10:01

\mathbold is math alphabet command (like \mathbf, \mathit etc) so it has no effect on < . \bm though does affect < and you get the character that the package sets up for \boldmath, If you add

\boldmath

$1 + 1 < 3\showlists$

You will see that \bm is selecting (in normal math) the fonts used in \boldname.

In this case that is

....\U/zeur/b/n/10 <

But as you show the bold font's < is a rather different shape to the medium weight font

So this appears to be a font issue.