The type signature of division in Haskell merely requires that it takes two fractional `a`s and returns another `a`. 1 / 0 :: Double evaluates to Infinity.

The type signature of division in Haskell merely requires that it takes two fractional `a`s and returns another `a`. 1 / 0 :: Double evaluates to Infinity. 1 / 0 :: Rational throws a runtime exception. A division by zero producing zero would be perfectly sensible in Haskell, and perhaps even desired if you are totally averse to runtime errors. The Pony language infamously does this.