Re: More /.{I->-1} craziness

*To*: mathgroup at smc.vnet.net*Subject*: [mg106530] Re: More /.{I->-1} craziness*From*: AES <siegman at stanford.edu>*Date*: Fri, 15 Jan 2010 03:20:58 -0500 (EST)*Organization*: Stanford University*References*: <hhhme6$o0s$1@smc.vnet.net>

In article <hhhme6$o0s$1 at smc.vnet.net>, Bob Hanlon <hanlonr at cox.net> wrote: > You appear to be comparing apples and oranges. > > Head /@ {I, E, Pi, Infinity} > > {Complex,Symbol,Symbol,DirectedInfinity} > > FullForm /@ {I, E, Pi, Infinity} > > {Complex[0,1],E,Pi,DirectedInfinity[1]} > > Since rules are applied to the FullForm,,, > > > Bob Hanlon Responses to this and many other similar responses in this thread: 1) The problem is not explaining _why_ or _how_ this behavior happens; the problem is that Mathematica has been constructed _so that it happens_ -- and it's a damaging and unfortunate and undesirable (and, at base, unnecessary?) way for Mathematica to respond. In other words, it's not necessarily a "bug" -- I don't have an opinion, or even qualifications to have an opinion, on that point -- but it's certainly a product defect.. 2) Quote from the primary Help for I: "The symbol I needs to be evaluated to become a complex number:" Huh? What? "The **symbol** I ...?" How many ordinary users of Mathematica do you think would view I, E and Pi as symbols that all happen to represent a number -- but that all function as symbols until you call for a numerical output? Put another way, how many users do you think would automatically know or expect, from their pre-Mathematica eduction that I, E and Pi would be handled in this different (inconsistent) way in Mathematica?