Why does SetPrecision not apply to 0?

Question

Is there a rationale why SetPrecision works on integers except for 0?

SetPrecision[1,5]

1.0000

SetPrecision[0,5]

0

Answer 1

If you have a value $x$ with an absolute uncertainty $dx$ the precision of $x$ is by definition:

$$\text{Precision}(x) = - \log_{10}(dx/x)$$

That is why for $x=0$ the precision is always infinity. You cannot change this by changing $dx$.

If you want to assign an absolute uncertainty to zero, you can set accuracy, which is defined as

$$\text{Accuracy}(x) =- \log_{10}(dx)$$

This can be done using SetAccuracy command:

SetAccuracy[0, 5]

0.*10^-5

Answer 2

From SetPrecision:

See also Precision and Accuracy.