ETeX is an alternative to standard ETeX. Where in TeX one writes \frac{1}{ n+1}", in ETeX one writes "frac(1, n+1)". The function transformETeX maps ETeX expressions to TeX expressions:

    transformETeX Dict.empty "frac(1, n+1)" == "\\frac{1}{ n+1}"

In addition, one has

     transformETeX Dict.empty "\\frac{1}{ n+1}" == "\\frac{1}{ n+1}"

Therefore a both TeX and ETeX expressions can be mixed freely