The numeric c types are (effectively) integral, too.

[Henning Thielemann]

On Wed, 27 Mar 2013, Jeff Shaw wrote:

> roundTo :: CTime -> CTime -> CTime
> roundTo a b = (a `div` b) * b
> 
> This works right now, but requires a trivial Integral class be written for every program that wants to do
> it.

Writing orphan instances is generally a bad idea. Instead you could put 
your roundTo function into a nice package and import it everywhere. I 
don't think that an Integral instance is the right way to go, since it 
would imply the signature:

div :: CTime -> CTime -> CTime

and the quotient of two time values is not a time.