Modulus/Remainder function for non-integers

Question

rem gives this:

Prelude> rem 9 8
1

I wanted something like this:

Prelude> nonIntRem 9.1 8
1.0999999999999996

I implemented it like this:

nonIntRem x y = x - (y * (fromIntegral $ truncate (x/y)))

My questions are:

1. Does something like this already exist in a standard Haskell library? I'd prefer to use a standard function, and I may have missed it.
2. If not, is there a more standard name for this function in other languages? Maybe fmod, but the behavior for negatives in this case is not like mod, but like rem. If there is no standard name, can you think of a better name for this function?
3. It seems to work properly, but if you notice a problem with this function, I'd like to know about it.

Answer 1

The function you're after is mod' from Data.Fixed.