round() rounds to an integer.
This is a popular request, for example #3472
digits(value, num_digits, num_decimals) rounds to num_digits and
num_decimals, left filled with spaces.
digits(value, num_digits) the same as digits(value, num_digits, 0)
Neither decimal separator nor any decimals after decimal separator
are emitted.
zdigits(...) is the same as digits(...) only left filled with zeros.
If the result does not fit num_digits, the result is never trimmed.
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