Its a very important feature of number theoretic functions that, although they may have a preferred format for input, they will accept a wealth...

It"s a very important feature of number theoretic functions that, although they may have a preferred format for input, they will accept a wealth of other different formats. We already saw this for nfinit which accepts either a polynomial or an nf. It will be true for ideals, ideles, congruence subgroups, etc. Ok, let"s stick with elements for the time being. How does one go from one representation to the other?