Class: LongDecimalRoundingMode::RoundingModeClass

Inherits:
Struct
  • Object
show all
Includes:
Comparable
Defined in:
lib/long-decimal.rb,
lib/long-decimal.rb

Overview

enumeration class to express the possible rounding modes that are supported by LongDecimal

Instance Method Summary collapse

Instance Method Details

#<=>(o) ⇒ Object

introduce some ordering for rounding modes



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# File 'lib/long-decimal.rb', line 146

def <=>(o)
  if o.respond_to?:num
    self.num <=> o.num
  elsif o.kind_of? Numeric
    self.num <=> o
  else
    puts("stack=#{caller.join("\n")}")
    raise TypeError, "o=#{o.inspect} must be numeric or RoundingMode";
  end
end

#ainverse ⇒ Object

inverse mode in terms of addition



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# File 'lib/long-decimal.rb', line 167

def ainverse
  LongDecimalRoundingMode::ADD_INVERSE_MODE[self]
end

#hash ⇒ Object 



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# File 'lib/long-decimal.rb', line 350

def hash
  num
end

#minverse ⇒ Object

inverse mode in terms of multiplication



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# File 'lib/long-decimal.rb', line 160

def minverse
  LongDecimalRoundingMode::MUL_INVERSE_MODE[self]
end

#pick_value(unrounded, sign, lower, upper, even) ⇒ Object

internal use no special checks included we assume: lower <= unrounded <= upper we assume: sign = sgn(unrounded)



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# File 'lib/long-decimal.rb', line 175

def pick_value(unrounded, sign, lower, upper, even)
  if (sign == 0 || major == MAJOR_UNNECESSARY)
    if (lower == unrounded)
      return lower
    elsif (upper == unrounded)
      return upper
    end
  end
  if (major == MAJOR_UP && sign > 0)
    return upper
  elsif (major == MAJOR_UP && sign < 0)
    return lower
  elsif (major == MAJOR_DOWN && sign > 0)
    return lower
  elsif (major == MAJOR_DOWN && sign < 0)
    return upper
  elsif (major == MAJOR_CEILING)
    return upper
  elsif (major == MAJOR_FLOOR)
    return lower
  elsif (major == MAJOR_UNNECESSARY)
    raise ArgumentError, "rounding #{name} of unrounded=#{unrounded} (sign=#{sign}) is not applicable for lower=#{lower} and upper=#{upper}"
  end
  on_boundary = false
  if (major == MAJOR_HALF)
    d = unrounded - lower <=> upper - unrounded
    if (d < 0)
      # unrounded is below half
      return lower
    elsif (d > 0)
      # unrounded is below half
      return upper
    else
      on_boundary = true
    end
  elsif (major == MAJOR_GEOMETRIC)
    prod = lower * upper
    if (prod < 0)
      raise ArgumentError, "geometric rounding #{name} of unrounded=#{unrounded} (sign=#{sign}) is not applicable for lower=#{lower} and upper=#{upper} with different signs"
    elsif (prod == 0)
      # lower or upper is 0
      # we only round 0 to 0
      if (sign == 0)
        raise ArgumentError, "geometric rounding #{name} of unrounded=#{unrounded} (sign=#{sign}) is not applicable for lower=#{lower} and upper=#{upper} with 0 cannot be decided"
      elsif (sign < 0)
        return lower
      else
        return upper
      end
    end
    # now prod > 0
    square = unrounded * unrounded
    d = square <=> prod
    if (d < 0)
      # |unrounded| < sqrt(lower*upper)
      if (sign < 0)
        # lower < unrounded < upper < 0
        return upper
      else
        # (sign > 0)
        return lower
      end
    elsif (d > 0)
      # |unrounded| > sqrt(lower*upper)
      if (sign < 0)
        # lower < unrounded < upper < 0
        return lower
      else
        # (sign > 0)
        return upper
      end
    else
      # (d == 0)
      on_boundary = true
    end
  elsif (major == MAJOR_HARMONIC)
    prod = lower * upper
    if (prod < 0)
      raise ArgumentError, "harmonic rounding #{name} of unrounded=#{unrounded} is not applicable for lower=#{lower} and upper=#{upper} with different signs"
    elsif (prod == 0)
      # lower or upper is 0
      # we only round 0 to 0
      if (sign == 0)
        raise ArgumentError, "harmonic rounding #{name} of unrounded=#{unrounded} is not applicable for lower=#{lower} and upper=#{upper} with 0 cannot be decided"
      elsif (sign < 0)
        return lower
      else
        return upper
      end
    end
    # now prod > 0
    # so either lower < unrounded < upper < 0
    # or 0 < lower < unrounded < upper
    sum = lower + upper
    lhs = unrounded * sum
    rhs = 2*prod
    d = lhs <=> rhs
    if (sign < 0)
      # lower + upper < 0
      d = -d
    end
    if (d < 0)
      # unrounded < 2*upper*lower/(upper+lower)
      return lower
    elsif (d > 0)
      # unrounded > 2*upper*lower/(upper+lower)
      return upper
    else
      # (d == 0)
      on_boundary = true
    end
  elsif (major == MAJOR_QUADRATIC)
    square = unrounded * unrounded
    lhs = 2 * square
    rhs = lower * lower + upper * upper
    d = lhs <=> rhs
    if (sign < 0)
      # lower <= unrounded <= upper <= 0
      # lower^2 >= unrounded >= upper^2 >= 0
      d = -d
    end
    if (d < 0)
      # unrounded < sqrt(...)
      return lower
    elsif (d > 0)
      # unrounded > sqrt(...)
      return upper
    else
      # (d == 0)
      on_boundary = true
    end
  elsif (major == MAJOR_CUBIC)
    cube = unrounded ** 3
    lhs = 2 * cube
    rhs = lower ** 3 + upper ** 3
    d = lhs <=> rhs
    if (d < 0)
      # unrounded < x_cubic(lower, upper)
      return lower
    elsif (d > 0)
      # unrounded > x_cubic(lower, upper)
      return upper
    else
      # (d == 0)
      on_boundary = true
    end
  else
    raise ArgumentError, "unsupported rounding mode (#{name}: major=#{major})"
  end
  if (! on_boundary)
    raise ArgumentError, "rounding #{name} of unrounded=#{unrounded} failed for lower=#{lower} and upper=#{upper}: not on boundary"
  end
  if (minor == MINOR_UP)
    return ROUND_UP.pick_value(unrounded, sign, lower, upper, even)
  elsif (minor == MINOR_DOWN)
    return ROUND_DOWN.pick_value(unrounded, sign, lower, upper, even)
  elsif (minor == MINOR_CEILING)
    return ROUND_CEILING.pick_value(unrounded, sign, lower, upper, even)
  elsif (minor == MINOR_FLOOR)
    return ROUND_FLOOR.pick_value(unrounded, sign, lower, upper, even)
  elsif (minor == MINOR_UNUSED)
    raise ArgumentError, "rounding #{name} of unrounded=#{unrounded} failed for lower=#{lower} and upper=#{upper}: on boundary but no applicable minor mode"
  elsif (minor == MINOR_EVEN)
    return even
  elsif (minor == MINOR_ODD)
    if (lower == even)
      return upper
    else
      return lower
    end
  else
    raise ArgumentError, "rounding #{name} of unrounded=#{unrounded} failed for lower=#{lower} and upper=#{upper}: on boundary but no applicable minor mode"
  end
end

#to_long_s ⇒ Object 



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# File 'lib/long-decimal.rb', line 354

def to_long_s
  "RM(#{name} major=#{major.name} minor=#{minor.name} num=#{num})"
end

#to_s ⇒ Object 



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# File 'lib/long-decimal.rb', line 358

def to_s
  "#{name}"
end