Re: Real roots and other assumptions...
- To: mathgroup at smc.vnet.net
- Subject: [mg19992] Re: Real roots and other assumptions...
- From: "Allan Hayes" <hay at haystack.demon.co.uk>
- Date: Thu, 23 Sep 1999 23:26:33 -0400
- References: <7s3p1u$ck5@smc.vnet.net> <7s796h$htf@smc.vnet.net> <7sc7u2$c66$1@dragonfly.wolfram.com>
- Sender: owner-wri-mathgroup at wolfram.com
Kevin J. McCann <kevin.mccann at jhuapl.edu> wrote in message news:7sc7u2$c66$1 at dragonfly.wolfram.com... > This does work > > Select[{(1 - E)^(1/3)}, Im[#1] == 0 & ] > {} > > as does this: > > Select[{(2. + I)*(2. - I)}, Im[#1] == 0 & ] > > which gives the odd-looking result > {5.+0.I} Kevin: This is because (2. + I)*(2. - I) 5. + 0.*I and 0. == 0 up to machine precision. Interestingly enough: 5. + 0.*I \[Element] Reals False -- snip-- Allan --------------------- Allan Hayes Mathematica Training and Consulting Leicester UK www.haystack.demon.co.uk hay at haystack.demon.co.uk Voice: +44 (0)116 271 4198 Fax: +44 (0)870 164 0565