Please explain to me the difference between the two computations:
lin=2*x - y + 2.0;lin(x=-11/9,y=-4/9)
-2.22044604925031e-16
and
2*(-11/9)-(-4/9)+2.000000000000000000
0.000000000000000000
It has to be a floating point computation, and I'm interested only in the sign of the outcome, which is why the first example gives me trouble.
I'm in 6.3. It doesn't automatically offer to update?
In sage 6.4.rc0, they give just the same for me. Which version of sage are you using ?
sage: var('x,y')
(x, y)
sage: lin = 2 * x - y + 2.0
sage: lin.parent()
Symbolic Ring
sage: lin(x=-11/9, y=-4/9)
0.000000000000000
sage: 2 * (-11/9) - (-4/9) + 2.0
0.000000000000000
Asked: 2014-10-31 20:56:22 +0100
Seen: 202 times
Last updated: Oct 31 '14
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Cannot confirm. In sage-6.2 this is both 0.000000000000.
I've had other examples. I'm new at this, so please tell me if there are specs (version, my computer or the like) where I can look for clues to fix this bug