[Tex/LaTex] Interpreting unicode ², ³, etc… characters in math mode

Question

Short question:

Is there some font encoding or other trick that would allow the unicode character ² (exponent 2) to be correctly interpreted by LaTeX, notably in math mode (i.e. translate it automatically into ^{2})?

(and likewise for ³, ⁴, …)

Detailed rationale:

Normally, to introduce an exponent in math mode one uses the ^ symbol, as in x^2 or e^{i\pi}. I've been using LaTeX for decades and this feels very natural. However, with my current setup, when I type the characters x ^ 2 on the keyboard, it results in the two unicode characters x².

I do have a \RequirePackage[utf8]{inputenc} around the beginning of my personal style file, and Unicode characters in general are interpreted correctly (accented characters and such).

Usually I think about it and do type x ^ ^ 2 which results in x^2, but often I'm typing fast and later have to go back to every line of code that produces a LaTeX Error: Command \texttwosuperior unavailable in en error. This is annoying.

I could implement a workaround at the level of my editor (I use vim, so it would be simple to add a mapping to convert the ² into ^2), but I'm wondering if there's a better editor-independent way to handle this.

Answer 1

ConTeXt does it right.

\starttext

x²³ and $x²³$

\stoptext

---

The same can be achieved with LaTeX and unicode-math.

\documentclass{article}
\usepackage{unicode-math}
\begin{document}
x²³ and $x²³$
\end{document}

---

In pdfLaTeX you have to use newunicodechar to redefine ² and ³ to make them math-mode aware.

\documentclass{article}
\usepackage[utf8]{inputenc}
\usepackage{textcomp} % for \text...superior
\usepackage{newunicodechar}
\newunicodechar{²}{\ifmmode{}^2\else\texttwosuperior\fi}
\newunicodechar{³}{\ifmmode{}^3\else\textthreesuperior\fi}
\begin{document}
x²³ and $x²³$
\end{document}