[Date Index]
[Thread Index]
[Author Index]
Re: Approximate Zero Times A Symbol
*To*: mathgroup at smc.vnet.net
*Subject*: [mg127113] Re: Approximate Zero Times A Symbol
*From*: Richard Fateman <fateman at cs.berkeley.edu>
*Date*: Sun, 1 Jul 2012 02:06:48 -0400 (EDT)
*Delivered-to*: l-mathgroup@mail-archive0.wolfram.com
*References*: <201206270811.EAA18698@smc.vnet.net> <19783652.3140.1340794328091.JavaMail.root@m06> <jsh3a9$sir$1@smc.vnet.net>
On 6/28/2012 1:06 AM, djmpark wrote:
....
The symbol x has a meaning, as one of
> the basic elements of the algebra, that the scalar 0.0 does not have. Using
> 0.0 x -> 0.0 changes the mathematical meaning of the expression.
>
This is certainly a useful discussion point. If x is "inches" then 0.0
* x still has a dimension (inches). If x is a vector, there is
possibly a distinction worth drawing between a zero vector and a scalar.
Etc.
On the other hand, 0.0 in Mathematica means something other than
mathematical zero in various versions of Mathematica. Though who can
tell about the future.
Try this.
h = 0.50000000000000000000000
Do[ h = 2*h - h}, {i, 1, 50}]
h
One might think that h, being 0. would have the property that h*x would
be 0. Also that h+1 would be 1. But you would be wrong.
In the version 8 Mathematica, numbers like that 0. are displayed in a
pink box, but of course there is no requirement that you print the
result, and if you utter If[h==0,yes,no] the answer is "yes".
So for programs it might as well be 0 if it is equal to 0.
Aside: The pink box is not quite the right size. Too small. My
suggestion (and implementation) was to display numbers with no
significant digits in red.
http://forums.wolfram.com/mathgroup/archive/2010/Jan/msg00897.html
I should have patented it :)
Prev by Date:
**Re: how to make a list of rules with 2 other lists composed by**
Next by Date:
**Re: Rearranging terms - user-defined**
Previous by thread:
**Re: how to make a list of rules with 2 other lists composed by**
Next by thread:
**Re: Approximate Zero Times A Symbol**
| |