R rounding explanation

Question

can any one please explain why this gives different outputs?

round(1.49999999999999)
1


round(1.4999999999999999)
2

I have read the round documentation but it does not mention anything about it there. I know that R represents numbers in binary form, but why does adding two extra 9's changes the result?

Thanks.

Answer 1

1.4999999999999999 can't be represented internally, so it gets rounded to 1.5.

Now, when you apply round(), the result is 2.