# If mathcode is used to typeset e and i upright, how to force it italics again?

I'm using \mathcode"69"69 in the preamble, as proposed in a comment in this question, to automatically typeset e and i upright in mathematical equations.

The question is, is there a way to get an italics i f.ex. as an index in math mode later? If so, how?

I tried $\mathit{i}$, which doesn't work.

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Commands can be defined using the old mathcode settings for i and e:

\documentclass{article}

\mathchardef\iti=\mathcode\i
\mathchardef\ite=\mathcode\e
\mathcode\i=\i
\mathcode\e=\e

\begin{document}

\begin{displaymath}
4 + 7i = 4e^{10} + b_\iti^\ite
\end{displaymath}

\end{document}


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