This is because in the code for rounding, an element's own round
method is tried before converting to a float. The round function for
rationals rounds up if its exactly halfway:
else:
q, r = self.numerator().quo_rem(self.denominator())
if r < self.denominator() / 2:
return q
else:
return q+1
To get consistent results you could use round(N()) instead. But
perhaps this should be considered a bug in the rational rounding. I'm
not sure if there is a standard convention for that, its clearly a
borderline case.
-Marshall Hampton
On Nov 29, 9:47 am, michel paul <[email protected]> wrote:
> sage: round(4.5)
> 5.0
> sage: round(9/2)
> 4.0
>
> I noticed some strange behavior in a graph and tried to narrow down the
> issue. This was it.
>
> --
> "Computer science is the new mathematics."
>
> -- Dr. Christos Papadimitriou
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