Method: Rational#round

Defined in:

rational.c

#round([ndigits][, half: mode]) ⇒ Integer

Returns rat rounded to the nearest value with a precision of ndigits decimal digits (default: 0).

When the precision is negative, the returned value is an integer with at least ndigits.abs trailing zeros.

Returns a rational when ndigits is positive, otherwise returns an integer.

Rational(3).round      #=> 3
Rational(2, 3).round   #=> 1
Rational(-3, 2).round  #=> -2

  #    decimal      -  1  2  3 . 4  5  6
  #                   ^  ^  ^  ^   ^  ^
  #   precision      -3 -2 -1  0  +1 +2

Rational('-123.456').round(+1).to_f  #=> -123.5
Rational('-123.456').round(-1)       #=> -120

The optional half keyword argument is available similar to Float#round.

Rational(25, 100).round(1, half: :up)    #=> (3/10)
Rational(25, 100).round(1, half: :down)  #=> (1/5)
Rational(25, 100).round(1, half: :even)  #=> (1/5)
Rational(35, 100).round(1, half: :up)    #=> (2/5)
Rational(35, 100).round(1, half: :down)  #=> (3/10)
Rational(35, 100).round(1, half: :even)  #=> (2/5)
Rational(-25, 100).round(1, half: :up)   #=> (-3/10)
Rational(-25, 100).round(1, half: :down) #=> (-1/5)
Rational(-25, 100).round(1, half: :even) #=> (-1/5)

Returns:

• (Integer)

# File 'rational.c', line 1542

static VALUE
nurat_round_n(int argc, VALUE *argv, VALUE self)
{
    VALUE opt;
    enum ruby_num_rounding_mode mode = (
        argc = rb_scan_args(argc, argv, "*:", NULL, &opt),
        rb_num_get_rounding_option(opt));
    VALUE (*round_func)(VALUE) = ROUND_FUNC(mode, nurat_round);
    return f_round_common(argc, argv, self, round_func);
}