Re: Re: Types in Mathematica thread

*To*: mathgroup at smc.vnet.net*Subject*: [mg62918] Re: [mg62877] Re: Types in Mathematica thread*From*: Andrzej Kozlowski <akoz at mimuw.edu.pl>*Date*: Thu, 8 Dec 2005 00:06:24 -0500 (EST)*References*: <dn38ft$3la$1@smc.vnet.net> <200512070412.XAA23854@smc.vnet.net>*Sender*: owner-wri-mathgroup at wolfram.com

On 7 Dec 2005, at 13:12, Jon Harrop wrote: > > RealQ[_Real] := True > RealQ[_] := False > > for equivalence with the Head test "_Real", rather than the > mathematical > concept of a real number. Of course this is not fool-proof: RealQ[_Real] := True RealQ[_] := False x=Real["I am not a number"]; RealQ[x] True One can, of course deal, with such perversity by: RealQ[x_Real] /; AtomQ[x] == True := True RealQ[_] := False or RealQ[x_Real] /; InexactNumberQ[x] == True := True RealQ[_] := False Andrzej Kozlowski

**References**:**Re: Types in Mathematica thread***From:*Jon Harrop <usenet@jdh30.plus.com>