[swift-evolution] Proposal: A standard library Fraction type

[Matthew Johnson]

> If your implementation of Rational simplifies immediately, sure. Mine doesn't and it is useful in many other cases not to as well. You might, for example, want to present the original numerator/denominator provided by the user.

How does your implementation implement equality?  From a numeric standpoint I think most people would consider 3/4 to be equal to 6/8 whereas this would not be correct for a time signature.  

In any case, I agree that a rational type would be a useful addition to the library.  I don't think I would use it to model time signatures but there are plenty of other uses.