What properties do you expect from such a mapping? When you go from integers to floats, the expectation is that the float type will have a wider range than the integer, so conversion is possible (at the price of losing precision).

Going in the other direction, this is impractical because floats have such a wide range.

I was mainly thinking of a map from integers to floats (in the context of axes of arrays), so that given a specific BigFloat range, I may choose the axis to be a BigInt range. I wasn’t thinking of conversion.

Of course, this only works if the floating-point type is integer-valued. If you want an approximate conversion, then you need to specify an approximation explicitly, e.g. via round: