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Re: Re: Types in Mathematica thread
*To*: mathgroup at smc.vnet.net
*Subject*: [mg62842] Re: [mg62839] Re: Types in Mathematica thread
*From*: Andrzej Kozlowski <akoz at mimuw.edu.pl>
*Date*: Tue, 6 Dec 2005 02:48:32 -0500 (EST)
*References*: <200512060543.AAA03708@smc.vnet.net>
*Sender*: owner-wri-mathgroup at wolfram.com
On 6 Dec 2005, at 14:43, Bill Rowe wrote:
> On 12/5/05 at 1:40 PM, akoz at mimuw.edu.pl (Andrzej Kozlowski) wrote:
>
>> On 5 Dec 2005, at 17:37, Kristen W Carlson wrote:
>
>>> I can't think of why there is no RealQ predicate, but there is
>>> _Real, a pattern test via the head.
>
>> Maybe because it is called InexactNumberQ.
>
> That clearly would not be the equivalent of RealQ since
> InexactNumberQ[Pi] correctly returns False when RealQ[Pi] would
> return True if it existed.
> --
The discussion was not about testing whether something is a real
number or not (in the mathematical sense). This you test with Element
[something, Reals]. The discussion was about "types". Please note the
title of the thread to which you have just contributed, or even
better rerad the thread. Well, the "type" of objects with head Real
in Mathematica is exactly what InexactNumberQ tests for. A
mathematica _Real is not a "real number" in the sense of mathematics
but precisely an "inexact number". (Actually, I myself do not agree
that that there are "types" in Mathematica and that these functions
test for "types". But even if it were not a discussion of "types" in
any case your answer would be quite wrong, since NumberQ[Pi] also
gives False, and surely Pi is a number? )
Andrzej Kozlowski
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