exact decimal type, was: 12.3*70.95 a little bit weird

How about rat(12.345678)?  Of course, ratepsilon should be 2e-15 or so
(which we agreed on in February 2005, but it's still 1e-8!) and you
probably want to turn off ratprint.

I really think the 999r9 notation is *extremely* special-purpose and not
worth adding.

As for fpprintprec, the only reason I know to print all digits is to ensure
that print/read is reversible.  Which is important, but shouldn't interfere
with ordinary use which doesn't need it.  What other reasons are there?

            -s

On Wed, Nov 30, 2011 at 11:55, Raymond Toy <toy.raymond at gmail.com> wrote:

>
>
> On Wed, Nov 30, 2011 at 6:33 AM, Stavros Macrakis <macrakis at alum.mit.edu>wrote:
>
>> This seems to add complexity where in fact simplicity is needed.
>>
>> The naive user who is confused by the trailing digits in 12.3*70.95 is
>> hardly likely to write 12.3r0*70.95r0.  And the sophisticated user
>> shouldn't find it too hard to write 123*10^-1 (3 extra keystrokes), and has
>> a variety of ways of controlling the form of the output.
>>
>
> I agree about the naive user.   I, however, would find 12.345678r0 to be
> quite handy because I invariably get the power of ten wrong.  And it
> doesn't bother me that a rational is printed out.  That's what "r" was
> intended to mean.
>
>>
>> Then there's the complication of output.  Do users who enter the fraction
>> 2/5 really want to see 4.0r-1 on output?  I doubt it.  But users who enter
>> 0.4r1 presumably don't want to see 2/5, either.  So then do we need to keep
>> track of the *origin* of each rat?  Do we want 2/5*3 to print as 6/5, but
>> 2/5*3r0 to print as 1.2r0?  Yuck yuck yuck.
>>
>
> Agreed.  It should just be a rational.
>
>>
>> This seems like a lot of complexity for a very simple problem.  The vast
>> majority of cases are, I suspect, handled satisfactorily by simply making
>> fpprintprec:14 by default.
>>
>
> I kind of disagree with that.  Floating point should be printed out to
> full precision;  changing fpprintprec merely hides the problem which the
> naive user should learn about and not be naive anymore.  The experienced
> user can set fpprintprec appropriately.
>
> Ray
>