\over not implemented

[expipiplus1]

It would be nice to have support for expressions such as:

{{1} \over {2}}

Here the \over command is used in an infix position between {1} and {2}.

Sadly a simple s/\\over/\\frac/g isn't a workaround due to the infix positioning.

[jgm]

Note that {1} {2} \over {3} is equivalent to \frac{{1} {2}}{3}, not {1} \frac{2}{3}.

[jgm]

Perhaps we could change formula so it stops at an \over and resumes again to parse the denominator.