Change spacing around binary operators

Question

I'd like to change spacing around binary operators and this issue is discussed there:
How to change default for spacing around binary relations?

Is there way how to change spacing in math and displaymath separately?

Answer 1

\everydisplay can be used to make a different setting for displayed equations:

\documentclass{article}

\medmuskip=0mu %    
\everydisplay{\medmuskip=10mu\relax}

\begin{document}
  \centering
  $a+b=c+d$
  \[ a+b=c+d\]
\end{document}