Re: Re: To be or not to be...

*To*: mathgroup at smc.vnet.net*Subject*: [mg62055] Re: [mg62032] Re: To be or not to be...*From*: Pratik Desai <pdesai1 at umbc.edu>*Date*: Thu, 10 Nov 2005 02:50:38 -0500 (EST)*References*: <dksd37$h58$1@smc.vnet.net> <200511091005.FAA19735@smc.vnet.net>*Sender*: owner-wri-mathgroup at wolfram.com

dh wrote: >Hi Ingolf, >the problem is not with Sequence, but with Equal and its brethren. >Sequence will simply insert an empty list into these functions. >We then have: > >Equal[] >Unequal[] >SameQ[] >UnsameQ[] > >the amazing fact is that all these are giving True. > >The closet thing one finds in the Help is: > >"Equal[e] gives True." > >and similar for the other functions. >Here e means an expression. To make ends meet, one has to assume that >"expression" in this context" can also mean "nothing" or no arguments. > > One the other hand an empty set in not the same as nothing, e.g. look at wikepedia's explanation of empty set http://en.wikipedia.org/wiki/Empty_set Or maybe I am missing something......won't be the first time :-) >The amazing thing here is, that in general, a pattern of f[x_] does not >fit f[]. Why should Equal be an exception??? > >sincerely, Daniel > >Ingolf Dahl wrote: > > >>To Mathgroup, >> >>Try the following commands in order: >> >>b = Sequence[] >> >>b == Sequence[] >> >>b != Sequence[] >> >>b === Sequence[] >> >>b =!= Sequence[] >> >>The four last lines all evaluate to "True" for me. Quite amazing! >> >>Best regards >> >>Ingolf Dahl >> >>Sweden >> >> >> >> >> > > > -- Pratik Desai Graduate Student UMBC Department of Mechanical Engineering Phone: 410 455 8134

**References**:**Re: To be or not to be...***From:*dh <dh@metrohm.ch>