Method: Integer#round

Defined in:

numeric.c

#round(ndigits = 0, half: :up) ⇒ Integer

Returns self rounded to the nearest value with a precision of ndigits decimal digits.

When ndigits is negative, the returned value has at least ndigits.abs trailing zeros:

555.round(-1)      # => 560
555.round(-2)      # => 600
555.round(-3)      # => 1000
-555.round(-2)     # => -600
555.round(-4)      # => 0

Returns self when ndigits is zero or positive.

555.round     # => 555
555.round(1)  # => 555
555.round(50) # => 555

If keyword argument half is given, and self is equidistant from the two candidate values, the rounding is according to the given half value:

• :up or nil: round away from zero:

  25.round(-1, half: :up)      # => 30
  (-25).round(-1, half: :up)   # => -30
  

• :down: round toward zero:

  25.round(-1, half: :down)    # => 20
  (-25).round(-1, half: :down) # => -20
  

• :even: round toward the candidate whose last nonzero digit is even:

  25.round(-1, half: :even)    # => 20
  15.round(-1, half: :even)    # => 20
  (-25).round(-1, half: :even) # => -20
  

Raises and exception if the value for half is invalid.

Related: Integer#truncate.

Returns:

• (Integer)

# File 'numeric.c', line 5780

static VALUE
int_round(int argc, VALUE* argv, VALUE num)
{
    int ndigits;
    int mode;
    VALUE nd, opt;

    if (!rb_scan_args(argc, argv, "01:", &nd, &opt)) return num;
    ndigits = NUM2INT(nd);
    mode = rb_num_get_rounding_option(opt);
    if (ndigits >= 0) {
        return num;
    }
    return rb_int_round(num, ndigits, mode);
}