Can you compare floating point values exactly to zero?

Question

I know we can\'t compare 2 floating point values using ==. We can only compare they are within some interval of each other. I know

if(val == 0.512)
         


        

Answer 1

Because zero does have an exact representation, it is possible for a value to compare == to zero. If the variable you are testing was set by an assignment, or from a value typed in (like getVal in your example?), it could easily be zero. But if it was the result of a calculation, the chances of it being exactly zero are very small. This is made worse because ordinary decimal fractions like 0.2 do not have an exact representation in floating point. That's why it's best to use epsilon.