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Marcin 'Qrczak' Kowalczyk <qrczak@xxxxxxxxxx> writes: >> So we need a way to query those questions. > > Querying is too late: when program needs a particular characteristic, > it doesn't help it that it could detect that the implementation > doesn't meet its expectations. Oh, so you want to demand that all Scheme systems must implement whatever feature you need for that program? How does that go? >> Scheme doesn't have "flonums" and that's a good and rational design >> choice. > > I disagree. There are programs which require flonums or something > which behave similarly. All Scheme implementations I know and all > other general-purpose languages I know provide flonums. No, Scheme does not provide "flonums". Some Scheme systems provide an implementation of inexact reals which is similar to the Lisp notion of a flonum. But that's not the same thing. > Consider the example at the end of R5RS run on a typical Scheme > implementation with floats and ratios, augmented with displaying all > elements of the lazy list it produces. It runs fine. But when we > replace the two inexact numbers in the initial state with exact ones > of the same values, fractions become bigger and bigger, even though > the growing precision it accumulates is useless: the algorithm is > inexact to begin with! But this is not a feature of exactness; it's a feature of the particular strategy chosen to implement exactness. (Which does not mean that I can imagine a different strategy!) So if you want to guarantee that the operation remain in constant size, and you recognize that mathematical division is not such an operation, you want a different operation: "constant size division". Constant size division preferences maintaining the implementation size of the result to mathematical correctness. > I want portable flonums. Do you care whether they are called "portable flonums"? Can we call them something else and you will be happy? I am suggesting that if what you care about is constant-size operations, that we provide mathematical operations that have that guarantee. Thomas