resistor_calculator.rb

gistfile1.rb

class ResistorCalculator
  # http://www.dannyg.com/examples/res2/resistor.htm

  attr_reader :tolerance, :multiplier, :ones, :tens, :ohms

  Tens       = %w[Black Brown Red Orange Yellow Green Blue Violet Gray White]
  Ones       = %w[Black Brown Red Orange Yellow Green Blue Violet Gray White]
  Multiplier = %w[Black Brown Red Orange Yellow Green Blue Violet Gray White Gold Silver]
  Tolerance  = %w[Gold Silver None]

  MultiplierValues = [ 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, -1, -2 ]
  ToleranceValues  = [ 5, 10, 20 ]

  def initialize(tens="Black", ones="Black", multiplier="Black", tolerance="Gold")
    @tens, @ones, @multiplier, @tolerance = *[tens, ones, multiplier, tolerance].map(&:capitalize)
    raise "Invalid Color #{@tens} for Tens"              unless Tens.include?(@tens)
    raise "Invalid Color #{@ones} for Ones"              unless Ones.include?(@ones)
    raise "Invalid Color #{@multiplier} for Multiplier"  unless Multiplier.include?(@multiplier)
    raise "Invalid Color #{@tolerance} for Tolerance"    unless Tolerance.include?(@tolerance)
    calculate_ohms
  end

  def calculate_ohms
    ohmage = (Tens.index(@tens) * 10.0) + Ones.index(@ones)
    @ohms = ohmage * (10**MultiplierValues[Multiplier.index(@multiplier)])
  end

  def to_f; calculate_ohms; end
  def to_i; calculate_ohms.to_i; end
  def to_s; "%s +/-%d%%" % [format(calculate_ohms), ToleranceValues[Tolerance.index(@tolerance)]]; end

  def inspect
    "Resistor.new(%s, %s, %s, %s) = %s" %
      [ @tens, @ones, @multiplier, @tolerance, to_s ]
  end

  def format(ohmage)
    if ohmage >= 1e6
      "%g Mohms" % (ohmage / 1e6)
    else
      ohmage >= 1e3 ? "%g Kohms" % (ohmage / 1e3) : "%g ohms" % ohmage
    end
  end

  def self.[](*a); new(*a).to_s; end

end

p ResistorCalculator["red", "red", "red", "gold"]

__END__
p ResistorCalculator.new("green", "green", "red", "gold").inspect
p ResistorCalculator.new("green", "green", "red", "gold").to_f
p ResistorCalculator.new("green", "green", "red", "gold").to_i
p ResistorCalculator.new("green", "green", "red", "gold").to_s
p ResistorCalculator["green", "green", "red", "gold"]
p ResistorCalculator["green", "green", "brown", "gold"]
p ResistorCalculator["green", "green", "gold", "gold"]
p ResistorCalculator["brown", "black", "red", "gold"]