\starttext

    $\displaystyle 1+{2g\over3}+{2\over3}$ \blank

    \setupmathfractions[topdistance=0pt]

    $\displaystyle 1+{2g\over3}+{2\over3}$ \blank

    \setupmathfractions[bottomdistance=0pt]

    $\displaystyle 1+{2g\over3}+{2\over3}$ \blank

    \setupmathfractions[topdistance=0pt,bottomdistance=0pt]

    $\displaystyle 1+{2g\over3}+{2\over3}$ \blank

\stoptext
