Class: Flt::FloatingTolerance

Inherits:
Tolerance show all
Defined in:
lib/flt/tolerance.rb

Overview

Implementation of floating tolerances

Class Method Summary collapse

Instance Method Summary collapse

Methods inherited from Tolerance

#[], big_epsilon, bits, #cast_value, decimals, define_sugar, #descr_value, digits, epsilon, #eq?, #equal_to?, #greater_than?, #gt?, #integer, #integer?, #less_than?, #lt?, #relative_to, #seq?, #value, #zero?

Constructor Details

#initialize(value, radix = :native) ⇒ FloatingTolerance

Returns a new instance of FloatingTolerance.



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# File 'lib/flt/tolerance.rb', line 316

def initialize(value, radix=:native)
  super(value)
  @radix = radix
end

Class Method Details

.float_minimum_normalized_fraction ⇒ Object 



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# File 'lib/flt/tolerance.rb', line 330

def self.float_minimum_normalized_fraction
  @float_minimum_normalized_fraction
end

.ref_adjusted_exp ⇒ Object 



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# File 'lib/flt/tolerance.rb', line 334

def self.ref_adjusted_exp
  -1
end

Instance Method Details

#relative_to_many(mode, *xs) ⇒ Object 



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# File 'lib/flt/tolerance.rb', line 338

def relative_to_many(mode, *xs)
  exp = nil

  num_class = xs.first.class
  context = num_class.context
  xs = xs.map{|x| x = context.Num(x); x.zero? ? context.minimum_normal(context.sign(x)) : x}
  v = cast_value(num_class)

  # TODO: simplify using context
  case xs.first
  when Flt::Num
    # TODO: handle special values
    if @radix == :native || @radix == num_class.radix
      exp = xs.map do |x|
        x = x.normalize
        exp = x.adjusted_exponent
        exp -= 1 if x.coefficient == x.num_class.context.minimum_normalized_coefficient # if :low mode
        exp -= FloatingTolerance.ref_adjusted_exp
        exp
      end.send(mode)
      r = num_class.Num(+1, v.coefficient, v.exponent+exp)
      r = r.normalize if num_class.radix == 2
      r
    elsif @radix==10
      # assert x.class==BinNum
      # TODO: optimize (implement log10 for BinNum)
      exp = xs.map do |x|
        x = x.to_decimal_exact(:exact=>true).normalize
        exp = x.adjusted_exponent
        exp -= 1 if x.coefficient == x.num_class.context.minimum_normalized_coefficient # if :low mode
        exp -= FloatingTolerance.ref_adjusted_exp
        exp
      end.send(mode)
      num_class.from_decimal(Flt.DecNum(+1, 1, exp)*v.to_decimal_exact)
    else
      # assert num_class==DecNum && @radix==2
      exp = xs.map do |x|
        exp = (x.ln/DecNum(2).ln).ceil.to_i - 1 # (x.ln/DecNum(2).ln).floor+1 - 1 if :high mode
        exp -= FloatingTolerance.ref_adjusted_exp
        exp
      end.send(mode)
      v*num_class.Num(2)**exp
    end
  when Float
    if @radix == :native || @radix == Float::RADIX
      exp = xs.map do |x|
        f,e = Math.frexp(x)
        exp = e-1
        exp -= 1 if f==FloatingTolerance.float_minimum_normalized_fraction # if :low mode
        exp -= FloatingTolerance.ref_adjusted_exp
      end.send(mode)
      Math.ldexp(v.to_f, exp)
    else
      # assert @radix==10
      exp = xs.map do |x|
        exp = Math.log10(x.abs).ceil - 1 # Math.log10(x.abs).floor+1 - 1 if :high mode
        exp -= FloatingTolerance.ref_adjusted_exp
      end.send(mode)
      v*10.0**exp
    end
  when BigDecimal
    if @radix == :native || @radix == 10
      exp = xs.map do |x|
        sign,digits,base,exp = x.split
        exp -= 1
        exp -= 1 if digits=="1" # if :low mode
        exp -= FloatingTolerance.ref_adjusted_exp
        exp
      end.send(mode)
      sign, digits, base, vexp = v.split
      BigDecimal.new("0.#{digits}E#{vexp+exp}")
    else
      # assert num_class==BigDecimal && @radix==2
      prec = 10
      exp = xs.map do |x|
        exp = (Flt::DecNum(x.to_s).ln/Flt::DecNum(2).ln).ceil - 1 # ... if :high mode
        exp -= FloatingTolerance.ref_adjusted_exp
        exp
      end.send(mode)
      context.Num(v)*context.Num(2)**exp
    end
  end
end

#to_s ⇒ Object 



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# File 'lib/flt/tolerance.rb', line 321

def to_s
  if @radix==:native
    "#{descr_value} flt."
  else
    "#{descr_value} flt.(#{radix})"
  end
end