# Evaluation question

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.

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