[Rd] abs() and negative output from fractions() (PR#3536)

[Prof Brian Ripley]

Something seems wrong in the way the group generics are registered, as 
they are not being called.  As a workaround, add

export(Math.fractions,Ops.fractions,Summary.fractions)

to library/MASS/NAMESPACE and the examples seem to work again.

On Wed, 23 Jul 2003, Barry Rowlingson wrote:

> Prof Brian Ripley wrote:
> > On Tue, 22 Jul 2003, Duncan Murdoch wrote:
> 
> > This is not even a VR bug: no one said abs() is implemented for fractions, 
> > and it is not.  From the help page:
> > 
> >      Arithmetic operations on `"fractions"' objects are possible.
> > 
> > and abs() is not such an operation.
> > 
> 
>   Something funny is happening with printing fractions - the values seem 
> correct under abs() [and other functions]:
> 
>  > xf
> [1]    2 -2/5  2/5  2/3
>  > abs(xf)
> [1]    2 -2/5  2/5  2/3
>  > abs(xf)[2]
> [1] 2/5
> 
>   huh?
> 
>  > sqrt(xf)
> [1]    2 -2/5  2/5  2/3
> Warning message:
> NaNs produced in: sqrt(xf)
> 
>  > sqrt(xf)[1:4]
> [1]   8119/5741         NaN     191/302 38804/47525
> Warning message:
> NaNs produced in: sqrt(xf)
> 
>   Bug, undocumented behaviour, feature? I dont know. It all seems to 
> work in 1.6.0, so everyone should downgrade now... :)
> 
> Baz
> 
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> 

-- 
Brian D. Ripley,                  ripley at stats.ox.ac.uk
Professor of Applied Statistics,  http://www.stats.ox.ac.uk/~ripley/
University of Oxford,             Tel:  +44 1865 272861 (self)
1 South Parks Road,                     +44 1865 272866 (PA)
Oxford OX1 3TG, UK                Fax:  +44 1865 272595