On Mon, 25 Feb 2008, Ben wrote:

<interactive>:1:8:

  Ambiguous type variable `t' in the constraints:

    `Fractional t' arising from a use of `/' at <interactive>:1:8-10

    `Integral t' arising from a use of `^' at <interactive>:1:7-15

  Probable fix: add a type signature that fixes these type variable(s)

/ doesn't do integer division, so from there it concludes that you're
working with a Fractional type - Haskell never coerces behind your back,
so not only the result of / but also its parameters are Fractional.

^ only works for Integral types. You might consider that a little
arbitrary, but hey - it's mostly like that because it's much easier to
raise something to an integer power.

There's no default it can pick that's both Fractional and Integral, so it
doesn't know what type the expression should have and it's asking you to
tell it ("add a type signature that fixes these type variable(s)"). In
practice you won't be able to unless you've got a broken number type
handy, but that's the way things go.

Ok, that makes sense.  There's no num k that's both Fractional and Integral, where as in the case where I had the number literals, those were two different instances. What's the usual way of working around this?  Something like

?