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*To*: John Cowan <cowan@x>*Subject*: Re: [Scheme-reports] result of (infinite? +nan.0+inf.0i)*From*: Alex Shinn <alexshinn@x>*Date*: Tue, 10 Sep 2013 21:22:43 +0900*Cc*: scheme-reports <scheme-reports@x>*In-reply-to*: <20130910114318.GG11797@mercury.ccil.org>*References*: <522EC4EA.1050903@bothner.com> <20130910114318.GG11797@mercury.ccil.org>

On Tue, Sep 10, 2013 at 8:43 PM, John Cowan <cowan@x> wrote:

Per Bothner scripsit:

It never has been. If you look at R6RS, you'll see that these predicates

> What should be the result of (infinite? +nan.0+inf.0i)? The report

> says #t but that seems undesirable, because it would mean that

> finite?/infinite?/nan? would no longer be a partitioning of the

> complex numbers,

are defined on real numbers only; the extension to complex numbers is

new in R7RS. The WG decided that the convention that a partly-infinite

complex number is an infinity and that a partly-NaN complex number is

a NaN was more important than extending the trichotomy.

There was some sentiment for declaring that any complex operation

that generated a partial NaN should generate a NaN, pure and simple,

but there were strong objections from the users of complex numbers,

who expected to be able to extract meaningful results from a partial NaN.

Well, the objections from "users of complex numbers" were

on both sides of the argument. In my case, at least, the

intention was merely to _allow_ implementations to generate

pure NaNs in place of partial NaNs, and the standard does

allow this.

More generally, neither NaNs nor complex numbers are

required by the standard, and implementations are allowed

to implement signaling NaNs which makes all this moot.

--

Alex

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**References**:**[Scheme-reports] result of (infinite? +nan.0+inf.0i)***From:*Per Bothner <per@x>

**Re: [Scheme-reports] result of (infinite? +nan.0+inf.0i)***From:*John Cowan <cowan@x>

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