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?