Incompatibility with acmart

[thirs]

Description

Unicode-math seems incompatible with acmart. Log message says:

!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
!
! LaTeX error: "kernel/command-already-defined"
! 
! Control sequence \not= already defined.
! 
! See the LaTeX3 documentation for further information.
! 
! For immediate help type H <return>.
!...............................................  

l.3853 \NewNegationCommand { = }    { \neq   }

Check/indicate

• [ X] Relevant for XeTeX
• [ ] Relevant for LuaTeX
• [ X] Issue tracker has been searched for similar issues?
• [ ] Links to discussion if appropriate

Minimal example demonstrating the issue

\documentclass{acmart}

\usepackage{fontspec}
\usepackage{unicode-math}

\begin{document}

\end{document}

Further details

[davidcarlisle]

actually you just need newtxmath You can undefine the commands to let unicode-math define them

\documentclass{article}
\usepackage{newtxmath}
\expandafter\let\csname not=\endcsname\relax
\expandafter\let\csname not<\endcsname\relax
\expandafter\let\csname not>\endcsname\relax
\usepackage{fontspec}
\usepackage{unicode-math}

\begin{document}

\end{document}

[wspr]

Hmm. Two comments/questions:

• Perhaps unicode-math should check for existence before trying to define its own. If anything, probably better to overwrite than throw an error.
• I should probably add \UndeclareNegation to handle this more flexibly.