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Re: "Sloppy Union"? (Union of a list with *nearly* equ

  • To: mathgroup at smc.vnet.net
  • Subject: [mg42171] Re: "Sloppy Union"? (Union of a list with *nearly* equ
  • From: Bill Rowe <listuser at earthlink.net>
  • Date: Sat, 21 Jun 2003 02:49:45 -0400 (EDT)
  • Sender: owner-wri-mathgroup at wolfram.com

On 6/20/03 at 4:57 AM, siegman at stanford.edu (AES/newspost) wrote:

> Still don't grasp, however, what SetPrecision with *reduced* precision 
> really does, or for what purpose it might be used?  For example,

>     SetPrecision[Pi,3] --> 3.14

>     Cos[y] --> -1.0

>     1 + y -> 4.14159
 
> Is it nothing more that a "print wrapper" for y, and nothing else?

No, it isn't a "print wrapper" for y at all. It defines the precision of y to be 3.

Try the following.

Precision[Cos@y] which results in 5.0057 in version 5.0
Precision[1 + y] which results in 3.12002 in version 5.0

Contrast this with

Precision[Cos@Pi] which results in Infinity or
Precison[1 + Pi] which results in Infinity

Note some versions of Mathematica default to displaying 6 digits for any number with a precision less than or equal to $MachinePrecision. It appears this as changed in version 5.0. I've only just started using version 5.0 and I am not yet familiar with many of the changes that have been made.


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