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| Date: Mon, 15 Aug 2005 09:38:34 -0700 | From: Per Bothner <per@xxxxxxxxxxx> | | Aubrey Jaffer wrote: | > I believe that the junking of 0/0 makes SRFI-70 compatible with | > IEEE-754. Do you agree? | | It's a bit awkward. The syntax 0/0 suggests 0/0 is exact. | The 0/0 syntax is extra awkward for an implementation that | defines 1/0 and -1/0 as exact infinities, as Kawa does. SRFI-70 specifies no Scheme notation for 0/0. It is used in the Specification to stand for a numeric error-object (or violation of implementation restriction). | (Exact infinites are an experimental addition in Kawa I won't claim | they're terribly well-specified or justified. I think they can be | useful in some situation, such as sentinel values.) | | I did find some discrepencies between your specification and Kawa: | | #|kawa:21|# (define neg-inf (/ -1.0 0.0)) | #|kawa:22|# neg-inf | #i-1/0 | #|kawa:23|# (log neg-inf) | #i1/0+3.141592653589793i | #|kawa:26|# (sqrt neg-inf) | #i+1/0i | | Kawa allows complex numbers with infinite components. | Whether this is "correct" or accidental I don't know. Non-real numbers with infinite components would all be SRFI-70 error-objects. But SRFI-70 needs to be clearer about this. | Also I got: | | #|kawa:30|# (angle neg-inf) | 0 The result should be pi, the same as (angle -1). | #|kawa:29|# (angle inf) | 0 If inf is inexact, then (angle inf) should be 0.0