Method: PerfectShape::Math.ieee754_remainder

Defined in:
lib/perfect_shape/math.rb

.ieee754_remainder(x, y) ⇒ Object Also known as: ieee_remainder

Computes the remainder operation on two arguments as prescribed by the IEEE 754 standard.

Algorithm is exactly: x – (round(x/y)*y)

The ‘round` part rounds to the nearest even number when it is a halfway between n & y (integer + 0.5 number)

The remainder value is mathematically equal to x - y × n, where n is the mathematical integer closest to the exact mathematical value of the quotient x/y, and if two mathematical integers are equally close to x/y, then n is the integer that is even. If the remainder is zero, its sign is the same as the sign of the first argument. Special cases:

If either argument is NaN, or the first argument is infinite, or the second argument is positive zero or negative zero, then the result is NaN.

If the first argument is finite and the second argument is infinite, then the result is the same as the first argument.

Parameters:

  • x —

    the dividend.

  • y —

    the divisor.

Returns:

  • the remainder when x is divided by y.



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# File 'lib/perfect_shape/math.rb', line 78

def ieee754_remainder(x, y)
  x = BigDecimal(x.to_s)
  y = BigDecimal(y.to_s)
  return BigDecimal::NAN if x.nan? || y.nan? || x.infinite? || y.zero?
  return x if x.finite? && y.infinite?
  division = x / y
  rounded_division_low = BigDecimal(division.floor)
  rounded_division_high = BigDecimal(division.ceil)
  rounded_division_half = rounded_division_low + 0.5
  rounded_division = if division == rounded_division_half
    rounded_division_low.to_i.even? ? rounded_division_low : rounded_division_high
  else
    BigDecimal(division.round)
  end
  (x - (rounded_division * y))
end