Re: [Maxima-discuss] SIGN1 strangeness, was: Problem with bfloat

[Richard F. <fa...@be...>]

On 9/1/2014 7:52 AM, David Billinghurst wrote:
> ... snip...



> , Maxima tries to convert it to bigfloat (I don't know what's the 
> purpose of that) and fails.
..

If you need to know the sign of  v  : sqrt(10^500+1)-10^250, how do you 
propose to
do this?

Here's one way...

fpprec:500$
sign(bfloat(v));

note that fpprec:499   is not enough, and gives "zero"  for the sign.


In general, the question of whether an expression is different from zero 
is recursively
undecidable.  This doesn't prevent us from solving the problem , in 
practice, most of the
time.  Just that you can expect some hairy problems to remain unsolved.