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| Date: Wed, 19 Oct 2005 07:47:30 -0400 (EDT) | From: Andre van Tonder <andre@xxxxxxxxxxxxxxxxx> | | On Tue, 18 Oct 2005, bear wrote: | | >> The bitwise operations operate on exact integers only. Should | >> they live in the section on exact arithmetic? Should they carry | >> ex prefixes? Or should they be extended to work on inexact | >> integers as well? | > | > I would say that having them operate on exact integers in the | > first place is questionable; These are operations on bit vectors, | > not operations on numbers, and their semantics require | > information (the vector length) which is not expressed by the | > numbers. To say that they are defined on numbers is to confuse | > the number with a particular representation. | | I share the discomfort with the bitwise operations. As far as I | can tell, the SRFI does not portably specify the value of | (BITWISE-NOT 42). SRFI-60 "Integers as Bits" defines the bitwise operations for all integers. And the reference implementation is written portably in R5RS Scheme. (BITWISE-NOT 42) ==> -43 | Are these operations truly going to be useful for portable | programs? Yes. In SLIB they are used for Byte/Number Conversions, Cyclic Checksum, Fast Fourier Transform, Space-Filling Curves, Portable Image Files, Random Numbers, and integer-sqrt.