range represents a range in which an exact value lies
Let range be a range of values, determined by some approximation
process, safely bounding an unknown value v. The command
roundcorrectly(range) determines a precision such that for this precision,
rounding to the nearest any value in range yields to the same
result, i.e. to the correct rounding of v.
If no such precision exists, a warning is displayed and roundcorrectly
evaluates to NaN.