This is regarding 'precision' state variable and floating point numbers.

When we round, say, a floating point number 1.15 in 100th place (round to nearest 10th), there can be two interpretations.

* Look at the floating point number represented by 1.15 and see if it's closer to 1.1 or 1.2. If we use binary flonums, the flonum represented by 1.15 is smaller than 115/100, so we print 1.1.

  Let's call this effective rounding.

* Take the notation 1.15 itself and apply elementary math.  We print 1.2.

  Let's call this notational rounding.