With GHCi, I get: Prelude Ratio> toRational (1.0/0) :: Ratio Integer 179769313486231590772930519078902473361797697894230657273430081157732675805500963132708477322407536021120113879871393357658789768814416622492847430639474124377767893424865485276302219601246094119453082952085005768838150682342462881473913110540827237163350510684586298239947245938479716304835356329624224137216 % 1 My personal gut feeling is that converting a NaN/Inf/etc to a fraction should be an error (although I see the point of being able to convert a e.g. Float to a Double and preserve such special values). Is it possible to provide a conversion function in the Floating or RealFloat class instead? -kzm -- If I haven't seen further, it is by standing in the footprints of giants