Nils,
> Date: Mon, 6 Jan 2014 13:18:07 -0800 (PST)
> From: Nils Bruin <nbr...@sfu.ca>
>
> On Monday, January 6, 2014 12:46:19 PM UTC-8, Zimmermann Paul wrote:
>
> > What about getting rid of real literals?
> >
>
> I think they exist mainly to let
>
> RealField(200)(1e-20)
>
> work in the first place: The parser needs to generate code to instantiate
> the constant 1e-20 somewhere and that constant should remember its original
> string representation to allow convenient creation of an element in
> RealField(200).
but RealField(200)("1e-20") already does the job:
sage: RealField(200)("1e-20")
1.0000000000000000000000000000000000000000000000000000000000e-20
> Consider for instance
>
> sage: RealField(200)(a+(1e-800))
> 9.9999999999999994515327145420957165172950370278739244710772e-21
>
> (adding this constant doesn't change the 53-bit representation of a but it
> does ensure the resulting number is not considered a RealLiteral any more).
this demonstrates another inconsistency:
sage: a=1e-20
sage: RealField(200)(a)
1.0000000000000000000000000000000000000000000000000000000000e-20
sage: RealField(200)(a+0)
9.9999999999999994515327145420957165172950370278739244710772e-21
sage: RealField(200)(1*a)
9.9999999999999994515327145420957165172950370278739244710772e-21
> So back to your question: I expect that real literals can't be removed
> because it would make creating high precision constants too much of a pain.
I don't think so. We should educate the user:
* if she/he writes 1e-20, she/he should be aware that (like in other languages)
1e-20 is not exactly representable in binary, thus will be approximated to
the current precision
* if she/he wants to define a high precision constant, use "1e-20"
Paul
--
You received this message because you are subscribed to the Google Groups
"sage-devel" group.
To unsubscribe from this group and stop receiving emails from it, send an email
to sage-devel+unsubscr...@googlegroups.com.
To post to this group, send email to sage-devel@googlegroups.com.
Visit this group at http://groups.google.com/group/sage-devel.
For more options, visit https://groups.google.com/groups/opt_out.
