\starttext

\definemathfraction[myfrac] [mathstyle=script]
\definemathfraction[myfracx][mathstyle=script,alternative=outer]

\startformula
{a^{2^{2^2}}\over a}
\frac{a^{2^{2^2}}}{a}
\frac{a^{2}}{b}
\myfrac{a^{2}}{b}
\myfracx{a^{2}}{b}
\stopformula

\stoptext
