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*To*: srfi-77@xxxxxxxxxxxxxxxxx*Subject*: multiplicative inverse of 0.0*From*: Aubrey Jaffer <agj@xxxxxxxxxxxx>*Date*: Sat, 22 Oct 2005 14:33:21 -0400 (EDT)*Delivered-to*: srfi-77@xxxxxxxxxxxxxxxxx*In-reply-to*: <20051022020312.GB5632@NYCMJCOWA2> (jcowan@xxxxxxxxxxxxxxxxx)*References*: <20051021145326.816C11B77BB@xxxxxxxxxxxxxxxxxxxxx> <20051021155906.GC16464@NYCMJCOWA2> <Pine.LNX.4.58.0510210910130.18969@xxxxxxxxxxxxxx> <20051022020312.GB5632@NYCMJCOWA2>

| procedure: expt z1 z2 | | Returns z1 raised to the power z2. For nonzero z1 | | z1^z2 = e^(z2 log z1) | | 0^z is 1 if z = 0, and 0 if `(real-part z)' is positive. | Otherwise, this procedure reports a violation of an | implementation restriction or returns an unspecified number. (expt x -1) is another way of writing (/ x); (expt x -2) is (/ (expt x 2)); etc. SRFI-77 specifies (/ 0.), but not (expt 0. -1). SRFI-70's treatment of EXPT is consistent with `/' in this regard. And this aspect was not controversial. For inexact arguments not both zero (define (expt z1 z2) (exp (* (if (zero? z1) (real-part z2) z2) (log z1)))) Why did SRFI-77 eschew SRFI-70's straightforward and safe generalization of EXPT to (returning) -inf.0? | (expt 5 3) ==> 125 | (expt 5 -3) ==> 1/125 | (expt 5 0) ==> 1 | (expt 0 5) ==> 0 | (expt 0 5+.0000312i) ==> 0 | (expt 0 -5) ==> unspecified | (expt 0 -5+.0000312i) ==> unspecified | (expt 0 0) ==> [sic] (expt 0 0) should return 1 (exact). There was a discussion about this for srfi-73 (http://srfi.schemers.org/srfi-73/mail-archive/msg00007.html through http://srfi.schemers.org/srfi-73/mail-archive/msg00011.html) and srfi-70 (http://srfi.schemers.org/srfi-70/mail-archive/msg00090.html). | (expt 0.0 0.0) ==> 1.0

**References**:**arithmetic issues***From:*Aubrey Jaffer

**Re: arithmetic issues***From:*John.Cowan

**Re: arithmetic issues***From:*bear

**Re: arithmetic issues***From:*John.Cowan

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