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Re: Nitpick with FLOOR etc.

This page is part of the web mail archives of SRFI 70 from before July 7th, 2015. The new archives for SRFI 70 contain all messages, not just those from before July 7th, 2015.

 | Date: Sat, 16 Jul 2005 05:12:13 -0400
 | From: Paul Schlie <schlie@xxxxxxxxxxx>
 | > From: Aubrey Jaffer <agj@xxxxxxxxxxxx>
 | > procedure        #i-/0            #i+/0
 | > =========        =====            =====
 | >
 | > floor            error           179.76931348623157e306
 | >
 | > ceiling  -179.76931348623157e306  error
 | >
 | > truncate -179.76931348623157e306 179.76931348623157e306
 | >
 | > round    -179.76931348623157e306 179.76931348623157e306
 | - it's not clear this is necessarily desirable?
 | As upon further thought it seems most reasonable that infinities
 | return infinities, or optionally throw an exception, for all such
 | scenarios to be most consistent?

If infinities are the only non-integers allowed to be returned from
these functions, should infinities be the only inexacts allowed to be
returned from `INEXACT->EXACT'?

 | (As otherwise the marginal error resulting from the conversion may
 | be infinite itself which seems inconsistent with the expectations
 | of the conversion.)

I grepped through SLIB and several Scheme applications' source for
occurrences of ROUND, CEILING, FLOOR, and TRUNCATE.  In essentially
all 30+ cases INEXACT->EXACT was called with the results of these
functions.  So having ROUND, CEILING, FLOOR, and TRUNCATE return
infinities will only slightly delay the exception.