Todd O'Bryan writes: > I just found a lovely Java expression to emphasize the inexactness of > doubles to my AP students. The problem--which I think is from > HtDP/1e--is to find the value of a bag of coins given the number of > pennies, nickels, dimes, and quarters. In BlueJ's code pad (or similar > in DrJava, jGrasp, etc.) > > > 0.01 + 0.05 + 0.10 + 0.25 > 0.410000000000000000003
That's a somewhat different problem: the impossibility of exact conversion between base-10 and base-2 floats. There isn't actually anything inexact about floating-point numbers, what is (at least potentially) inexact is *operations* on floating-point numbers. So the precise definition of Scheme's concept of an inexact number is "a number that might be the result of an inexact operation". What's particularly nasty in the example you show is that the operation that causes the inexactness, base conversion, is implicit. Konrad. ____________________ Racket Users list: http://lists.racket-lang.org/users
