Jerzy Karczmarczuk writes:

I am abhorred by the fact that adding ... :: Rational changes the lexical meaning of a literal.

It doesn't. A literal with a decimal point always means (fromRational (X%Y)) for some appropriate X and Y. Adding a type signature changes the dynamic meaning of the literal, not the lexical meaning (something we're used to in Haskell, no?). Cheers, Simon