Class: RubyUnits::Unit

Inherits:
Numeric show all
Includes:
Comparable
Defined in:
lib/ruby_units/unit.rb,
lib/ruby_units/cache.rb,
lib/ruby_units/version.rb,
lib/ruby_units/definition.rb

Defined Under Namespace

Modules: Version Classes: Cache, Definition

Constant Summary collapse

VERSION = 
Unit::Version::STRING
UNITY = 
'<1>'
UNITY_ARRAY = 
[UNITY]
FEET_INCH_UNITS_REGEX =

ideally we would like to generate this regex from the alias for a ‘feet’ and ‘inches’, but they aren’t defined at the point in the code where we need this regex.

/(?:'|ft|feet)\s*(\d+)\s*(?:"|in|inch(?:es)?)/
FEET_INCH_REGEX = 
/(\d+)\s*#{FEET_INCH_UNITS_REGEX}/
LBS_OZ_UNIT_REGEX =

ideally we would like to generate this regex from the alias for a ‘pound’ and ‘ounce’, but they aren’t defined at the point in the code where we need this regex.

/(?:#|lbs?|pounds?|pound-mass)+[\s,]*(\d+)\s*(?:ozs?|ounces?)/
LBS_OZ_REGEX = 
/(\d+)\s*#{LBS_OZ_UNIT_REGEX}/
TIME_REGEX = 
/(\d+)*:(\d+)*:*(\d+)*[:,]*(\d+)*/
SCI_NUMBER = 
%r{([+-]?\d*[.]?\d+(?:[Ee][+-]?)?\d*)}
RATIONAL_NUMBER = 
/\(?([+-])?(\d+[ -])?(\d+)\/(\d+)\)?/
COMPLEX_NUMBER = 
/#{SCI_NUMBER}?#{SCI_NUMBER}i\b/
NUMBER_REGEX = 
/#{SCI_NUMBER}*\s*(.+)?/
UNIT_STRING_REGEX = 
/#{SCI_NUMBER}*\s*([^\/]*)\/*(.+)*/
TOP_REGEX = 
/([^ \*]+)(?:\^|\*\*)([\d-]+)/
BOTTOM_REGEX = 
/([^* ]+)(?:\^|\*\*)(\d+)/
NUMBER_UNIT_REGEX = 
/#{SCI_NUMBER}?(.*)/
COMPLEX_REGEX = 
/#{COMPLEX_NUMBER}\s?(.+)?/
RATIONAL_REGEX = 
/#{RATIONAL_NUMBER}\s?(.+)?/
KELVIN = 
['<kelvin>']
FAHRENHEIT = 
['<fahrenheit>']
RANKINE = 
['<rankine>']
CELSIUS = 
['<celsius>']
SIGNATURE_VECTOR = 
[
    :length,
    :time,
    :temperature,
    :mass,
    :current,
    :substance,
    :luminosity,
    :currency,
    :information,
    :angle
]
@@definitions = 
{}
@@PREFIX_VALUES = 
{}
@@PREFIX_MAP = 
{}
@@UNIT_MAP = 
{}
@@UNIT_VALUES = 
{}
@@UNIT_REGEX = 
nil
@@UNIT_MATCH_REGEX = 
nil
@@TEMP_REGEX = 
nil
@@KINDS = 
{
    -312078      => :elastance,
    -312058      => :resistance,
    -312038      => :inductance,
    -152040      => :magnetism,
    -152038      => :magnetism,
    -152058      => :potential,
    -7997        => :specific_volume,
    -79          => :snap,
    -59          => :jolt,
    -39          => :acceleration,
    -38          => :radiation,
    -20          => :frequency,
    -19          => :speed,
    -18          => :viscosity,
    -17          => :volumetric_flow,
    -1           => :wavenumber,
    0            => :unitless,
    1            => :length,
    2            => :area,
    3            => :volume,
    20           => :time,
    400          => :temperature,
    7941         => :yank,
    7942         => :power,
    7959         => :pressure,
    7962         => :energy,
    7979         => :viscosity,
    7961         => :force,
    7981         => :momentum,
    7982         => :angular_momentum,
    7997         => :density,
    7998         => :area_density,
    8000         => :mass,
    152020       => :radiation_exposure,
    159999       => :magnetism,
    160000       => :current,
    160020       => :charge,
    312058       => :conductance,
    312078       => :capacitance,
    3199980      => :activity,
    3199997      => :molar_concentration,
    3200000      => :substance,
    63999998     => :illuminance,
    64000000     => :luminous_power,
    1280000000   => :currency,
    25600000000  => :information,
    511999999980 => :angular_velocity,
    512000000000 => :angle
}
@@cached_units = 
{}
@@base_unit_cache = 
{}

Instance Attribute Summary collapse

Class Method Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(*options) ⇒ Unit

Create a new Unit object. Can be initialized using a String, a Hash, an Array, Time, DateTime

Examples:

Valid options include:

"5.6 kg*m/s^2"
"5.6 kg*m*s^-2"
"5.6 kilogram*meter*second^-2"
"2.2 kPa"
"37 degC"
"1"  -- creates a unitless constant with value 1
"GPa"  -- creates a unit with scalar 1 with units 'GPa'
"6'4\"""  -- recognized as 6 feet + 4 inches
"8 lbs 8 oz" -- recognized as 8 lbs + 8 ounces
[1, 'kg']
{:scalar => 1, :numerator=>'kg'}

Parameters:

Raises:

  • (ArgumentError) —

    if absolute value of a temperature is less than absolute zero

  • (ArgumentError) —

    if no unit is specified

  • (ArgumentError) —

    if an invalid unit is specified



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# File 'lib/ruby_units/unit.rb', line 284

def initialize(*options)
  @scalar      = nil
  @base_scalar = nil
  @unit_name   = nil
  @signature   = nil
  @output      = {}
  raise ArgumentError, "Invalid Unit Format" if options[0].nil?
  if options.size == 2
    # options[0] is the scalar
    # options[1] is a unit string
    begin
      cached = @@cached_units[options[1]] * options[0]
      copy(cached)
    rescue
      initialize("#{options[0]} #{(options[1].units rescue options[1])}")
    end
    return
  end
  if options.size == 3
    options[1] = options[1].join if options[1].kind_of?(Array)
    options[2] = options[2].join if options[2].kind_of?(Array)
    begin
      cached = @@cached_units["#{options[1]}/#{options[2]}"] * options[0]
      copy(cached)
    rescue
      initialize("#{options[0]} #{options[1]}/#{options[2]}")
    end
    return
  end

  case options[0]
    when Unit
      copy(options[0])
      return
    when Hash
      @scalar      = options[0][:scalar] || 1
      @numerator   = options[0][:numerator] || UNITY_ARRAY
      @denominator = options[0][:denominator] || UNITY_ARRAY
      @signature   = options[0][:signature]
    when Array
      initialize(*options[0])
      return
    when Numeric
      @scalar    = options[0]
      @numerator = @denominator = UNITY_ARRAY
    when Time
      @scalar      = options[0].to_f
      @numerator   = ['<second>']
      @denominator = UNITY_ARRAY
    when DateTime, Date
      @scalar      = options[0].ajd
      @numerator   = ['<day>']
      @denominator = UNITY_ARRAY
    when /^\s*$/
      raise ArgumentError, "No Unit Specified"
    when String
      parse(options[0])
    else
      raise ArgumentError, "Invalid Unit Format"
  end
  self.update_base_scalar
  raise ArgumentError, "Temperatures must not be less than absolute zero" if self.is_temperature? && self.base_scalar < 0
  unary_unit = self.units || ""
  if options.first.instance_of?(String)
    opt_scalar, opt_units = RubyUnits::Unit.parse_into_numbers_and_units(options[0])
    unless @@cached_units.keys.include?(opt_units) ||
        (opt_units =~ %r{\D/[\d+\.]+}) ||
        (opt_units =~ /(#{RubyUnits::Unit.temp_regex})|(#{LBS_OZ_UNIT_REGEX})|(#{FEET_INCH_UNITS_REGEX})|%|(#{TIME_REGEX})|i\s?(.+)?|&plusmn;|\+\/-/)
      @@cached_units[opt_units] = (self.scalar == 1 ? self : opt_units.to_unit) if opt_units && !opt_units.empty?
    end
  end
  unless @@cached_units.keys.include?(unary_unit) || (unary_unit =~ /#{RubyUnits::Unit.temp_regex}/) then
    @@cached_units[unary_unit] = (self.scalar == 1 ? self : unary_unit.to_unit)
  end
  [@scalar, @numerator, @denominator, @base_scalar, @signature, @is_base].each { |x| x.freeze }
  return self
end

Instance Attribute Details

#base_denominator ⇒ Array

Returns:



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# File 'lib/ruby_units/unit.rb', line 235

def base_denominator
  @base_denominator
end

#base_numerator ⇒ Array

Returns:



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# File 'lib/ruby_units/unit.rb', line 232

def base_numerator
  @base_numerator
end

#base_scalar ⇒ Numeric

Returns:



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# File 'lib/ruby_units/unit.rb', line 229

def base_scalar
  @base_scalar
end

#denominator ⇒ Array

Returns:



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# File 'lib/ruby_units/unit.rb', line 223

def denominator
  @denominator
end

#numerator ⇒ Array

Returns:



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# File 'lib/ruby_units/unit.rb', line 220

def numerator
  @numerator
end

#output ⇒ String

Returns:



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# File 'lib/ruby_units/unit.rb', line 238

def output
  @output
end

#scalar ⇒ Numeric

Returns:



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# File 'lib/ruby_units/unit.rb', line 217

def scalar
  @scalar
end

#signature ⇒ Integer

Returns:

  • (Integer) 


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# File 'lib/ruby_units/unit.rb', line 226

def signature
  @signature
end

#unit_name ⇒ String

Returns:



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# File 'lib/ruby_units/unit.rb', line 241

def unit_name
  @unit_name
end

Class Method Details

.base_unit_cache ⇒ Hash

Returns:

  • (Hash) 


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# File 'lib/ruby_units/unit.rb', line 386

def self.base_unit_cache
  return @@base_unit_cache
end

.cached ⇒ Hash

Returns:

  • (Hash) 


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# File 'lib/ruby_units/unit.rb', line 371

def self.cached
  return @@cached_units
end

.clear_cache ⇒ true

Returns:

  • (true) 


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# File 'lib/ruby_units/unit.rb', line 377

def self.clear_cache
  @@cached_units    = {}
  @@base_unit_cache = {}
  RubyUnits::Unit.new(1)
  return true
end

.define(unit_definition, &block) ⇒ RubyUnits::Unit::Definition

Unpack a unit definition and add it to the array of defined units

Examples:

Block form

RubyUnits::Unit.define('foobar') do |foobar|
  foobar.definition = RubyUnits::Unit.new("1 baz")
end

RubyUnits::Unit::Definition form

unit_definition = RubyUnits::Unit::Definition.new("foobar") {|foobar| foobar.definition = RubyUnits::Unit.new("1 baz")}
RubyUnits::Unit.define(unit_definition)

Parameters:

Returns:

Raises:

  • (ArgumentError) —

    when passed a non-string if using the block form



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# File 'lib/ruby_units/unit.rb', line 181

def self.define(unit_definition, &block)
  if block_given?
    raise ArgumentError, "When using the block form of RubyUnits::Unit.define, pass the name of the unit" unless unit_definition.instance_of?(String)
    unit_definition = RubyUnits::Unit::Definition.new(unit_definition, &block)
  end
  RubyUnits::Unit.definitions[unit_definition.name] = unit_definition
  RubyUnits::Unit.use_definition(unit_definition)
  return unit_definition
end

.defined?(unit) ⇒ Boolean

determine if a unit is already defined

Parameters:

Returns:

  • (Boolean) 


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# File 'lib/ruby_units/unit.rb', line 149

def self.defined?(unit)
  self.definitions.values.any? { |d| d.aliases.include?(unit) }
end

.definition(_unit) ⇒ RubyUnits::Unit::Definition?

return the unit definition for a unit

Parameters:

Returns:



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# File 'lib/ruby_units/unit.rb', line 156

def self.definition(_unit)
  unit = (_unit =~ /^<.+>$/) ? _unit : "<#{_unit}>"
  return @@definitions[unit]
end

.definitions ⇒ Array

return a list of all defined units

Returns:



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# File 'lib/ruby_units/unit.rb', line 163

def self.definitions
  return @@definitions
end

.parse(input) ⇒ Unit

Examples:

parse strings

"1 minute in seconds"

Parameters:

Returns:



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# File 'lib/ruby_units/unit.rb', line 394

def self.parse(input)
  first, second = input.scan(/(.+)\s(?:in|to|as)\s(.+)/i).first
  second.nil? ? RubyUnits::Unit.new(first) : RubyUnits::Unit.new(first).convert_to(second)
end

.redefine!(name) {|RubyUnits::Unit::Definition| ... } ⇒ RubyUnits::Unit::Definition

Get the definition for a unit and allow it to be redefined

Parameters:

  • name (String) —

    Name of unit to redefine

  • block (Block)

Yields:

Returns:

Raises:

  • (ArgumentError) —

    if a block is not given



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# File 'lib/ruby_units/unit.rb', line 197

def self.redefine!(name)
  fail ArgumentError, 'A block is required to redefine a unit' unless block_given?
  unit_definition = definition(name)
  yield unit_definition
  @@definitions.delete("<#{name}>")
  define(unit_definition)
  RubyUnits::Unit.setup
end

.setup ⇒ true

setup internal arrays and hashes

Returns:

  • (true) 


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# File 'lib/ruby_units/unit.rb', line 127

def self.setup
  self.clear_cache
  @@PREFIX_VALUES    = {}
  @@PREFIX_MAP       = {}
  @@UNIT_VALUES      = {}
  @@UNIT_MAP         = {}
  @@UNIT_REGEX       = nil
  @@UNIT_MATCH_REGEX = nil
  @@PREFIX_REGEX     = nil

  @@definitions.each do |name, definition|
    self.use_definition(definition)
  end

  RubyUnits::Unit.new(1)
  return true
end

.undefine!(unit) ⇒ true

Undefine a unit. Will not raise an exception for unknown units.

Parameters:

  • name (String) —

    of unit to undefine

Returns:

  • (true) 


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# File 'lib/ruby_units/unit.rb', line 209

def self.undefine!(unit)
  @@definitions.delete("<#{unit}>")
  RubyUnits::Unit.setup
end

Instance Method Details

#%(other) ⇒ Integer

perform a modulo on a unit, will raise an exception if the units are not compatible

Parameters:

  • other (Object)

Returns:

  • (Integer) 


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# File 'lib/ruby_units/unit.rb', line 801

def %(other)
  return self.divmod(other).last
end

#*(other) ⇒ Unit

Multiply two units.

Parameters:

Returns:

Raises:

  • (ArgumentError) —

    when attempting to multiply two temperatures



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# File 'lib/ruby_units/unit.rb', line 746

def *(other)
  case other
    when Unit
      raise ArgumentError, "Cannot multiply by temperatures" if [other, self].any? { |x| x.is_temperature? }
      opts = RubyUnits::Unit.eliminate_terms(@scalar*other.scalar, @numerator + other.numerator, @denominator + other.denominator)
      opts.merge!(:signature => @signature + other.signature)
      return RubyUnits::Unit.new(opts)
    when Numeric
      return RubyUnits::Unit.new(:scalar => @scalar*other, :numerator => @numerator, :denominator => @denominator, :signature => @signature)
    else
      x, y = coerce(other)
      return x * y
  end
end

#**(other) ⇒ Unit

Exponentiate. Only takes integer powers. Note that anything raised to the power of 0 results in a Unit object with a scalar of 1, and no units. Throws an exception if exponent is not an integer. Ideally this routine should accept a float for the exponent It should then convert the float to a rational and raise the unit by the numerator and root it by the denominator but, sadly, floats can’t be converted to rationals.

For now, if a rational is passed in, it will be used, otherwise we are stuck with integers and certain floats < 1

Parameters:

Returns:

Raises:

  • (ArgumentError) —

    when raising a temperature to a power

  • (ArgumentError) —

    when n not in the set integers from (1..9)

  • (ArgumentError) —

    when attempting to raise to a complex number

  • (ArgumentError) —

    when an invalid exponent is passed



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# File 'lib/ruby_units/unit.rb', line 819

def **(other)
  raise ArgumentError, "Cannot raise a temperature to a power" if self.is_temperature?
  if other.kind_of?(Numeric)
    return self.inverse if other == -1
    return self if other == 1
    return 1 if other.zero?
  end
  case other
    when Rational
      return self.power(other.numerator).root(other.denominator)
    when Integer
      return self.power(other)
    when Float
      return self**(other.to_i) if other == other.to_i
      valid = (1..9).map { |x| 1/x }
      raise ArgumentError, "Not a n-th root (1..9), use 1/n" unless valid.include? other.abs
      return self.root((1/other).to_int)
    when Complex
      raise ArgumentError, "exponentiation of complex numbers is not yet supported."
    else
      raise ArgumentError, "Invalid Exponent"
  end
end

#+(other) ⇒ Unit

Add two units together. Result is same units as receiver and scalar and base_scalar are updated appropriately throws an exception if the units are not compatible. It is possible to add Time objects to units of time

Parameters:

  • other (Object)

Returns:

Raises:

  • (ArgumentError) —

    when two temperatures are added

  • (ArgumentError) —

    when units are not compatible

  • (ArgumentError) —

    when adding a fixed time or date to a time span



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# File 'lib/ruby_units/unit.rb', line 674

def +(other)
  case other
    when Unit
      case
        when self.zero?
          other.dup
        when self =~ other
          raise ArgumentError, "Cannot add two temperatures" if ([self, other].all? { |x| x.is_temperature? })
          if [self, other].any? { |x| x.is_temperature? }
            if self.is_temperature?
              RubyUnits::Unit.new(:scalar => (self.scalar + other.convert_to(self.temperature_scale).scalar), :numerator => @numerator, :denominator => @denominator, :signature => @signature)
            else
              RubyUnits::Unit.new(:scalar => (other.scalar + self.convert_to(other.temperature_scale).scalar), :numerator => other.numerator, :denominator => other.denominator, :signature => other.signature)
            end
          else
            @q ||= ((@@cached_units[self.units].scalar / @@cached_units[self.units].base_scalar) rescue (self.units.to_unit.to_base.scalar))
            RubyUnits::Unit.new(:scalar => (self.base_scalar + other.base_scalar)*@q, :numerator => @numerator, :denominator => @denominator, :signature => @signature)
          end
        else
          raise ArgumentError, "Incompatible Units ('#{self}' not compatible with '#{other}')"
      end
    when Date, Time
      raise ArgumentError, "Date and Time objects represent fixed points in time and cannot be added to a Unit"
    else
      x, y = coerce(other)
      y + x
  end
end

#-(other) ⇒ Unit

Subtract two units. Result is same units as receiver and scalar and base_scalar are updated appropriately

Parameters:

Returns:

Raises:

  • (ArgumentError) —

    when subtracting a temperature from a degree

  • (ArgumentError) —

    when units are not compatible

  • (ArgumentError) —

    when subtracting a fixed time from a time span



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# File 'lib/ruby_units/unit.rb', line 709

def -(other)
  case other
    when Unit
      case
        when self.zero?
          if other.zero?
            other.dup * -1 # preserve Units class
          else
            -other.dup
          end
        when self =~ other
          case
            when [self, other].all? { |x| x.is_temperature? }
              RubyUnits::Unit.new(:scalar => (self.base_scalar - other.base_scalar), :numerator => KELVIN, :denominator => UNITY_ARRAY, :signature => @signature).convert_to(self.temperature_scale)
            when self.is_temperature?
              RubyUnits::Unit.new(:scalar => (self.base_scalar - other.base_scalar), :numerator => ['<tempK>'], :denominator => UNITY_ARRAY, :signature => @signature).convert_to(self)
            when other.is_temperature?
              raise ArgumentError, "Cannot subtract a temperature from a differential degree unit"
            else
              @q ||= ((@@cached_units[self.units].scalar / @@cached_units[self.units].base_scalar) rescue (self.units.to_unit.scalar/self.units.to_unit.to_base.scalar))
              RubyUnits::Unit.new(:scalar => (self.base_scalar - other.base_scalar)*@q, :numerator => @numerator, :denominator => @denominator, :signature => @signature)
          end
        else
          raise ArgumentError, "Incompatible Units ('#{self}' not compatible with '#{other}')"
      end
    when Time
      raise ArgumentError, "Date and Time objects represent fixed points in time and cannot be subtracted from to a Unit, which can only represent time spans"
    else
      x, y = coerce(other)
      return y-x
  end
end

#-@ ⇒ Numeric, Unit

negates the scalar of the Unit

Returns:



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# File 'lib/ruby_units/unit.rb', line 1066

def -@
  return -@scalar if self.unitless?
  return (self.dup * -1)
end

#/(other) ⇒ Unit

Divide two units. Throws an exception if divisor is 0

Parameters:

Returns:

Raises:

  • (ZeroDivisionError) —

    if divisor is zero

  • (ArgumentError) —

    if attempting to divide a temperature by another temperature



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# File 'lib/ruby_units/unit.rb', line 767

def /(other)
  case other
    when Unit
      raise ZeroDivisionError if other.zero?
      raise ArgumentError, "Cannot divide with temperatures" if [other, self].any? { |x| x.is_temperature? }
      opts = RubyUnits::Unit.eliminate_terms(@scalar/other.scalar, @numerator + other.denominator, @denominator + other.numerator)
      opts.merge!(:signature => @signature - other.signature)
      return RubyUnits::Unit.new(opts)
    when Numeric
      raise ZeroDivisionError if other.zero?
      return RubyUnits::Unit.new(:scalar => @scalar/other, :numerator => @numerator, :denominator => @denominator, :signature => @signature)
    else
      x, y = coerce(other)
      return y / x
  end
end

#<=>(other) ⇒ -1|0|1|nil

Compare two Unit objects. Throws an exception if they are not of compatible types. Comparisons are done based on the value of the unit in base SI units.

Parameters:

  • other (Object)

Returns:

  • (-1|0|1|nil)

Raises:

  • (NoMethodError) —

    when other does not define <=>

  • (ArgumentError) —

    when units are not compatible



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# File 'lib/ruby_units/unit.rb', line 575

def <=>(other)
  case
    when !self.base_scalar.respond_to?(:<=>)
      raise NoMethodError, "undefined method `<=>' for #{self.base_scalar.inspect}"
    when other.nil?
      return self.base_scalar <=> nil
    when !self.is_temperature? && other.respond_to?(:zero?) && other.zero?
      return self.base_scalar <=> 0
    when other.instance_of?(Unit)
      raise ArgumentError, "Incompatible Units ('#{self.units}' not compatible with '#{other.units}')" unless self =~ other
      return self.base_scalar <=> other.base_scalar
    else
      x, y = coerce(other)
      return y <=> x
  end
end

#==(other) ⇒ Boolean

Compare Units for equality this is necessary mostly for Complex units. Complex units do not have a <=> operator so we define this one here so that we can properly check complex units for equality. Units of incompatible types are not equal, except when they are both zero and neither is a temperature Equality checks can be tricky since round off errors may make essentially equivalent units appear to be different.

Parameters:

  • other (Object)

Returns:

  • (Boolean) 


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# File 'lib/ruby_units/unit.rb', line 600

def ==(other)
  case
    when other.respond_to?(:zero?) && other.zero?
      return self.zero?
    when other.instance_of?(Unit)
      return false unless self =~ other
      return self.base_scalar == other.base_scalar
    else
      begin
        x, y = coerce(other)
        return x == y
      rescue ArgumentError # return false when object cannot be coerced
        return false
      end
  end
end

#===(other) ⇒ Boolean Also known as: same?, same_as?

Compare two units. Returns true if quantities and units match

Examples:

RubyUnits::Unit.new("100 cm") === RubyUnits::Unit.new("100 cm")   # => true
RubyUnits::Unit.new("100 cm") === RubyUnits::Unit.new("1 m")      # => false

Parameters:

  • other (Object)

Returns:

  • (Boolean) 


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# File 'lib/ruby_units/unit.rb', line 649

def ===(other)
  case other
    when Unit
      (self.scalar == other.scalar) && (self.units == other.units)
    else
      begin
        x, y = coerce(other)
        return x === y
      rescue ArgumentError
        return false
      end
  end
end

#=~(other) ⇒ Boolean Also known as: compatible?, compatible_with?

Note:

if you want to do a regexp comparison of the unit string do this … unit.units =~ /regexp/

check to see if units are compatible, but not the scalar part this check is done by comparing signatures for performance reasons if passed a string, it will create a unit object with the string and then do the comparison

Examples:

this permits a syntax like:

unit =~ "mm"

Parameters:

  • other (Object)

Returns:

  • (Boolean) 


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# File 'lib/ruby_units/unit.rb', line 626

def =~(other)
  case other
    when Unit
      self.signature == other.signature
    else
      begin
        x, y = coerce(other)
        return x =~ y
      rescue ArgumentError
        return false
      end
  end
end

#abs ⇒ Numeric, Unit

absolute value of a unit

Returns:



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# File 'lib/ruby_units/unit.rb', line 1073

def abs
  return @scalar.abs if self.unitless?
  return RubyUnits::Unit.new(@scalar.abs, @numerator, @denominator)
end

#ago ⇒ Unit

Examples:

‘5 min’.to_unit.ago

Returns:



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# File 'lib/ruby_units/unit.rb', line 1151

def ago
  return self.before
end

#as_json(*args) ⇒ String

Returns string formatted for json

Returns:



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# File 'lib/ruby_units/unit.rb', line 1013

def as_json(*args)
  to_s
end

#before(time_point = ::Time.now) ⇒ Unit Also known as: before_now

Examples:

‘5 min’.before(time)

Returns:



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# File 'lib/ruby_units/unit.rb', line 1157

def before(time_point = ::Time.now)
  case time_point
    when Time, Date, DateTime
      return (time_point - self rescue time_point.to_datetime - self)
    else
      raise ArgumentError, "Must specify a Time, Date, or DateTime"
  end
end

#best_prefix ⇒ Object

returns a new unit that has been scaled to be more in line with typical usage.



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# File 'lib/ruby_units/unit.rb', line 1230

def best_prefix
  return self.to_base if self.scalar == 0
  _best_prefix =  if (self.kind == :information)
    @@PREFIX_VALUES.key(2**((Math.log(self.base_scalar,2) / 10.0).floor * 10))
  else
    @@PREFIX_VALUES.key(10**((Math.log10(self.base_scalar) / 3.0).floor * 3))
  end
  self.to(RubyUnits::Unit.new(@@PREFIX_MAP.key(_best_prefix)+self.units(false)))
end

#ceil ⇒ Numeric, Unit

ceil of a unit

Returns:



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# File 'lib/ruby_units/unit.rb', line 1080

def ceil
  return @scalar.ceil if self.unitless?
  return RubyUnits::Unit.new(@scalar.ceil, @numerator, @denominator)
end

#coerce(other) ⇒ Array

automatically coerce objects to units when possible if an object defines a ‘to_unit’ method, it will be coerced using that method

Parameters:

Returns:



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# File 'lib/ruby_units/unit.rb', line 1217

def coerce(other)
  if other.respond_to? :to_unit
    return [other.to_unit, self]
  end
  case other
    when Unit
      return [other, self]
    else
      return [RubyUnits::Unit.new(other), self]
  end
end

#convert_to(other) ⇒ Unit Also known as: >>, to

Note:

If temperature is part of a compound unit, the temperature will be treated as a differential and the units will be scaled appropriately.

convert to a specified unit string or to the same units as another Unit

unit.convert_to "kg"   will covert to kilograms
unit1.convert_to unit2 converts to same units as unit2 object

To convert a Unit object to match another Unit object, use:

unit1 >>= unit2

Special handling for temperature conversions is supported. If the Unit object is converted from one temperature unit to another, the proper temperature offsets will be used. Supports Kelvin, Celsius, Fahrenheit, and Rankine scales.

Parameters:

  • other (Object)

Returns:

Raises:

  • (ArgumentError) —

    when attempting to convert a degree to a temperature

  • (ArgumentError) —

    when target unit is unknown

  • (ArgumentError) —

    when target unit is incompatible



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# File 'lib/ruby_units/unit.rb', line 921

def convert_to(other)
  return self if other.nil?
  return self if TrueClass === other
  return self if FalseClass === other
  if (Unit === other && other.is_temperature?) || (String === other && other =~ /temp[CFRK]/)
    raise ArgumentError, "Receiver is not a temperature unit" unless self.degree?
    start_unit = self.units
    target_unit = other.units rescue other
    unless @base_scalar
      @base_scalar = case @@UNIT_MAP[start_unit]
                       when '<tempC>'
                         @scalar + 273.15
                       when '<tempK>'
                         @scalar
                       when '<tempF>'
                         (@scalar+459.67)*Rational(5, 9)
                       when '<tempR>'
                         @scalar*Rational(5, 9)
                     end
    end
    q= case @@UNIT_MAP[target_unit]
         when '<tempC>'
           @base_scalar - 273.15
         when '<tempK>'
           @base_scalar
         when '<tempF>'
           @base_scalar * Rational(9, 5) - 459.67
         when '<tempR>'
           @base_scalar * Rational(9, 5)
       end
    return RubyUnits::Unit.new("#{q} #{target_unit}")
  else
    case other
      when Unit
        return self if other.units == self.units
        target = other
      when String
        target = RubyUnits::Unit.new(other)
      else
        raise ArgumentError, "Unknown target units"
    end
    raise ArgumentError, "Incompatible Units ('#{self}' not compatible with '#{other}')" unless self =~ target
    _numerator1   = @numerator.map { |x| @@PREFIX_VALUES[x] ? @@PREFIX_VALUES[x] : x }.map { |i| i.kind_of?(Numeric) ? i : @@UNIT_VALUES[i][:scalar] }.compact
    _denominator1 = @denominator.map { |x| @@PREFIX_VALUES[x] ? @@PREFIX_VALUES[x] : x }.map { |i| i.kind_of?(Numeric) ? i : @@UNIT_VALUES[i][:scalar] }.compact
    _numerator2   = target.numerator.map { |x| @@PREFIX_VALUES[x] ? @@PREFIX_VALUES[x] : x }.map { |x| x.kind_of?(Numeric) ? x : @@UNIT_VALUES[x][:scalar] }.compact
    _denominator2 = target.denominator.map { |x| @@PREFIX_VALUES[x] ? @@PREFIX_VALUES[x] : x }.map { |x| x.kind_of?(Numeric) ? x : @@UNIT_VALUES[x][:scalar] }.compact

    q = @scalar * ((_numerator1 + _denominator2).inject(1) { |product, n| product*n }) /
        ((_numerator2 + _denominator1).inject(1) { |product, n| product*n })
    return RubyUnits::Unit.new(:scalar => q, :numerator => target.numerator, :denominator => target.denominator, :signature => target.signature)
  end
end

#copy(from) ⇒ Unit

Used to copy one unit to another

Parameters:

  • from (Unit) —

    Unit to copy definition from

Returns:



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# File 'lib/ruby_units/unit.rb', line 253

def copy(from)
  @scalar      = from.scalar
  @numerator   = from.numerator
  @denominator = from.denominator
  @is_base     = from.is_base?
  @signature   = from.signature
  @base_scalar = from.base_scalar
  @unit_name = from.unit_name rescue nil
  return self
end

#divmod(other) ⇒ Array

divide two units and return quotient and remainder when both units are in the same units we just use divmod on the raw scalars otherwise we use the scalar of the base unit which will be a float

Parameters:

  • other (Object)

Returns:

Raises:

  • (ArgumentError) 


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# File 'lib/ruby_units/unit.rb', line 789

def divmod(other)
  raise ArgumentError, "Incompatible Units ('#{self}' not compatible with '#{other}')" unless self =~ other
  if self.units == other.units
    return self.scalar.divmod(other.scalar)
  else
    return self.to_base.scalar.divmod(other.to_base.scalar)
  end
end

#floor ⇒ Numeric, Unit

Returns:



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# File 'lib/ruby_units/unit.rb', line 1086

def floor
  return @scalar.floor if self.unitless?
  return RubyUnits::Unit.new(@scalar.floor, @numerator, @denominator)
end

#from(time_point) ⇒ Time, ... Also known as: after, from_now

Examples:

‘5 min’.from(time)

Parameters:

Returns:

Raises:

  • (ArgumentError) —

    when passed argument is not a Time, Date, or DateTime



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# File 'lib/ruby_units/unit.rb', line 1201

def from(time_point)
  case time_point
    when Time, DateTime, Date
      return (time_point + self rescue time_point.to_datetime + self)
    else
      raise ArgumentError, "Must specify a Time, Date, or DateTime"
  end
end

#inspect(dump = nil) ⇒ String

Deprecated.

Normally pretty prints the unit, but if you really want to see the guts of it, pass ‘:dump’

Returns:



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# File 'lib/ruby_units/unit.rb', line 532

def inspect(dump = nil)
  return super() if dump
  to_s
end

#inverse ⇒ Unit

returns inverse of Unit (1/unit)

Returns:



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# File 'lib/ruby_units/unit.rb', line 898

def inverse
  return RubyUnits::Unit.new("1") / self
end

#is_base? ⇒ Boolean Also known as: base?

Is this unit in base form?

Returns:

  • (Boolean) 


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# File 'lib/ruby_units/unit.rb', line 408

def is_base?
  return @is_base if defined? @is_base
  @is_base = (@numerator + @denominator).compact.uniq.
      map { |unit| RubyUnits::Unit.definition(unit) }.
      all? { |element| element.unity? || element.base? }
  return @is_base
end

#is_degree? ⇒ Boolean Also known as: degree?

true if a degree unit or equivalent.

Returns:

  • (Boolean) 


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# File 'lib/ruby_units/unit.rb', line 548

def is_degree?
  return self.kind == :temperature
end

#is_temperature? ⇒ Boolean Also known as: temperature?

TODO:

use unit definition to determine if it’s a temperature instead of a regex

true if unit is a ‘temperature’, false if a ‘degree’ or anything else

Returns:

  • (Boolean) 


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# File 'lib/ruby_units/unit.rb', line 540

def is_temperature?
  return self.is_degree? && (!(@@UNIT_MAP[self.units] =~ /temp[CFRK]/).nil?)
end

#kind ⇒ Symbol

@todo: figure out how to handle :counting units. This method should probably return :counting instead of :unitless for ‘each’ return the kind of the unit (:mass, :length, etc…)

Returns:

  • (Symbol) 


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# File 'lib/ruby_units/unit.rb', line 365

def kind
  return @@KINDS[self.signature]
end

#kind_of?(klass) ⇒ Boolean

needed to make complex units play nice – otherwise not detected as a complex_generic

Parameters:

  • (Class)

Returns:

  • (Boolean) 


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# File 'lib/ruby_units/unit.rb', line 246

def kind_of?(klass)
  self.scalar.kind_of?(klass)
end

#power(n) ⇒ Unit

returns the unit raised to the n-th power

Parameters:

  • n (Integer)

Returns:

Raises:

  • (ArgumentError) —

    when attempting to raise a temperature to a power

  • (ArgumentError) —

    when n is not an integer



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# File 'lib/ruby_units/unit.rb', line 848

def power(n)
  raise ArgumentError, "Cannot raise a temperature to a power" if self.is_temperature?
  raise ArgumentError, "Exponent must an Integer" unless n.kind_of?(Integer)
  return self.inverse if n == -1
  return 1 if n.zero?
  return self if n == 1
  if n > 0 then
    return (1..(n-1).to_i).inject(self) { |product, x| product * self }
  else
    return (1..-(n-1).to_i).inject(self) { |product, x| product / self }
  end
end

#pred ⇒ Unit

returns previous unit in a range. ‘2 mm’.to_unit.pred #=> ‘1 mm’.to_unit only works when the scalar is an integer

Returns:

Raises:

  • (ArgumentError) —

    when scalar is not equal to an integer



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# File 'lib/ruby_units/unit.rb', line 1118

def pred
  raise ArgumentError, "Non Integer Scalar" unless @scalar == @scalar.to_i
  return RubyUnits::Unit.new(@scalar.to_i.pred, @numerator, @denominator)
end

#root(n) ⇒ Unit

Calculates the n-th root of a unit if n < 0, returns 1/unit^(1/n)

Parameters:

  • n (Integer)

Returns:

Raises:

  • (ArgumentError) —

    when attemptint to take the root of a temperature

  • (ArgumentError) —

    when n is not an integer

  • (ArgumentError) —

    when n is 0



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# File 'lib/ruby_units/unit.rb', line 868

def root(n)
  raise ArgumentError, "Cannot take the root of a temperature" if self.is_temperature?
  raise ArgumentError, "Exponent must an Integer" unless n.kind_of?(Integer)
  raise ArgumentError, "0th root undefined" if n.zero?
  return self if n == 1
  return self.root(n.abs).inverse if n < 0

  vec = self.unit_signature_vector
  vec =vec.map { |x| x % n }
  raise ArgumentError, "Illegal root" unless vec.max == 0
  num = @numerator.dup
  den = @denominator.dup

  for item in @numerator.uniq do
    x = num.find_all { |i| i==item }.size
    r = ((x/n)*(n-1)).to_int
    r.times { |y| num.delete_at(num.index(item)) }
  end

  for item in @denominator.uniq do
    x = den.find_all { |i| i==item }.size
    r = ((x/n)*(n-1)).to_int
    r.times { |y| den.delete_at(den.index(item)) }
  end
  q = @scalar < 0 ? (-1)**Rational(1, n) * (@scalar.abs)**Rational(1, n) : @scalar**Rational(1, n)
  return RubyUnits::Unit.new(:scalar => q, :numerator => num, :denominator => den)
end

#round(ndigits = 0) ⇒ Numeric, Unit

Returns:



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# File 'lib/ruby_units/unit.rb', line 1092

def round(ndigits = 0)
  return @scalar.round(ndigits) if self.unitless?
  return RubyUnits::Unit.new(@scalar.round(ndigits), @numerator, @denominator)
end

#since(time_point) ⇒ Unit

Examples:

‘min’.since(time)

Parameters:

Returns:

Raises:

  • (ArgumentError) —

    when time point is not a Time, Date, or DateTime



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# File 'lib/ruby_units/unit.rb', line 1172

def since(time_point)
  case time_point
  when Time
    return (Time.now - time_point).to_unit('s').convert_to(self)
  when DateTime, Date
    return (DateTime.now - time_point).to_unit('d').convert_to(self)
  else
    fail ArgumentError, 'Must specify a Time, Date, or DateTime'
  end
end

#succ ⇒ Unit Also known as: next

returns next unit in a range. ‘1 mm’.to_unit.succ #=> ‘2 mm’.to_unit only works when the scalar is an integer

Returns:

Raises:

  • (ArgumentError) —

    when scalar is not equal to an integer



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# File 'lib/ruby_units/unit.rb', line 1107

def succ
  raise ArgumentError, "Non Integer Scalar" unless @scalar == @scalar.to_i
  return RubyUnits::Unit.new(@scalar.to_i.succ, @numerator, @denominator)
end

#temperature_scale ⇒ String

returns the ‘degree’ unit associated with a temperature unit

Examples:

‘100 tempC’.to_unit.temperature_scale #=> ‘degC’

Returns:

  • (String) —

    possible values: degC, degF, degR, or degK



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# File 'lib/ruby_units/unit.rb', line 557

def temperature_scale
  return nil unless self.is_temperature?
  return "deg#{@@UNIT_MAP[self.units][/temp([CFRK])/, 1]}"
end

#to_base ⇒ Unit Also known as: base

TODO:

this is brittle as it depends on the display_name of a unit, which can be changed

convert to base SI units results of the conversion are cached so subsequent calls to this will be fast

Returns:



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# File 'lib/ruby_units/unit.rb', line 422

def to_base
  return self if self.is_base?
  if @@UNIT_MAP[self.units] =~ /\A<(?:temp|deg)[CRF]>\Z/
    @signature = @@KINDS.key(:temperature)
    base = case
             when self.is_temperature?
               self.convert_to('tempK')
             when self.is_degree?
               self.convert_to('degK')
           end
    return base
  end

  cached = ((@@base_unit_cache[self.units] * self.scalar) rescue nil)
  return cached if cached

  num = []
  den = []
  q   = 1
  for unit in @numerator.compact do
    if @@PREFIX_VALUES[unit]
      q *= @@PREFIX_VALUES[unit]
    else
      q *= @@UNIT_VALUES[unit][:scalar] if @@UNIT_VALUES[unit]
      num << @@UNIT_VALUES[unit][:numerator] if @@UNIT_VALUES[unit] && @@UNIT_VALUES[unit][:numerator]
      den << @@UNIT_VALUES[unit][:denominator] if @@UNIT_VALUES[unit] && @@UNIT_VALUES[unit][:denominator]
    end
  end
  for unit in @denominator.compact do
    if @@PREFIX_VALUES[unit]
      q /= @@PREFIX_VALUES[unit]
    else
      q /= @@UNIT_VALUES[unit][:scalar] if @@UNIT_VALUES[unit]
      den << @@UNIT_VALUES[unit][:numerator] if @@UNIT_VALUES[unit] && @@UNIT_VALUES[unit][:numerator]
      num << @@UNIT_VALUES[unit][:denominator] if @@UNIT_VALUES[unit] && @@UNIT_VALUES[unit][:denominator]
    end
  end

  num = num.flatten.compact
  den = den.flatten.compact
  num = UNITY_ARRAY if num.empty?
  base = RubyUnits::Unit.new(RubyUnits::Unit.eliminate_terms(q, num, den))
  @@base_unit_cache[self.units]=base
  return base * @scalar
end

#to_c ⇒ Complex

converts the unit back to a complex if it is unitless. Otherwise raises an exception

Returns:

  • (Complex)

Raises:

  • (RuntimeError) —

    when not unitless



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# File 'lib/ruby_units/unit.rb', line 988

def to_c
  return Complex(@scalar) if self.unitless?
  raise RuntimeError, "Cannot convert '#{self.to_s}' to Complex unless unitless.  Use Unit#scalar"
end

#to_date ⇒ Date

Returns:



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# File 'lib/ruby_units/unit.rb', line 1139

def to_date
  return Date.new0(self.convert_to('d').scalar)
end

#to_datetime ⇒ DateTime

convert a duration to a DateTime. This will work so long as the duration is the duration from the zero date defined by DateTime

Returns:

  • (DateTime) 


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# File 'lib/ruby_units/unit.rb', line 1134

def to_datetime
  return DateTime.new!(self.convert_to('d').scalar)
end

#to_f ⇒ Float

converts the unit back to a float if it is unitless. Otherwise raises an exception

Returns:

  • (Float)

Raises:

  • (RuntimeError) —

    when not unitless



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# File 'lib/ruby_units/unit.rb', line 980

def to_f
  return @scalar.to_f if self.unitless?
  raise RuntimeError, "Cannot convert '#{self.to_s}' to Float unless unitless.  Use Unit#scalar"
end

#to_i ⇒ Integer Also known as: to_int

if unitless, returns an int, otherwise raises an error

Returns:

  • (Integer)

Raises:

  • (RuntimeError) —

    when not unitless



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# File 'lib/ruby_units/unit.rb', line 996

def to_i
  return @scalar.to_int if self.unitless?
  raise RuntimeError, "Cannot convert '#{self.to_s}' to Integer unless unitless.  Use Unit#scalar"
end

#to_r ⇒ Rational

if unitless, returns a Rational, otherwise raises an error

Returns:

  • (Rational)

Raises:

  • (RuntimeError) —

    when not unitless



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# File 'lib/ruby_units/unit.rb', line 1006

def to_r
  return @scalar.to_r if self.unitless?
  raise RuntimeError, "Cannot convert '#{self.to_s}' to Rational unless unitless.  Use Unit#scalar"
end

#to_s(target_units = nil) ⇒ String

Generate human readable output. If the name of a unit is passed, the unit will first be converted to the target unit before output. some named conversions are available

You can also pass a standard format string (i.e., ‘%0.2f’) or a strftime format string.

output is cached so subsequent calls for the same format will be fast

Examples:

unit.to_s(:ft) - outputs in feet and inches (e.g., 6'4")
unit.to_s(:lbs) - outputs in pounds and ounces (e.g, 8 lbs, 8 oz)

Parameters:

  • target_units (Symbol) (defaults to: nil)

Returns:



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# File 'lib/ruby_units/unit.rb', line 485

def to_s(target_units=nil)
  out = @output[target_units]
  if out
    return out
  else
    case target_units
    when :ft
      inches = self.convert_to("in").scalar.to_int
      out    = "#{(inches / 12).truncate}\'#{(inches % 12).round}\""
    when :lbs
      ounces = self.convert_to("oz").scalar.to_int
      out    = "#{(ounces / 16).truncate} lbs, #{(ounces % 16).round} oz"
    when String
      out = case target_units.strip
            when /\A\s*\Z/ # whitespace only
              ''
            when /(%[\-+\.\w#]+)\s*(.+)*/ #format string like '%0.2f in'
              begin
                if $2 #unit specified, need to convert
                  self.convert_to($2).to_s($1)
                else
                  "#{$1 % @scalar} #{$2 || self.units}".strip
                end
              rescue # parse it like a strftime format string
                (DateTime.new(0) + self).strftime(target_units)
              end
            when /(\S+)/ #unit only 'mm' or '1/mm'
              self.convert_to($1).to_s
            else
              raise "unhandled case"
            end
    else
      out = case @scalar
            when Rational, Complex
              "#{@scalar} #{self.units}"
            else
              "#{'%g' % @scalar} #{self.units}"
            end.strip
    end
    @output[target_units] = out
    return out
  end
end

#to_time ⇒ Time Also known as: time

Tries to make a Time object from current unit. Assumes the current unit hold the duration in seconds from the epoch.

Returns:



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# File 'lib/ruby_units/unit.rb', line 1125

def to_time
  return Time.at(self)
end

#to_unit ⇒ Unit Also known as: unit

Returns:



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# File 'lib/ruby_units/unit.rb', line 400

def to_unit
  self
end

#truncate ⇒ Numeric, Unit

Returns:



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# File 'lib/ruby_units/unit.rb', line 1098

def truncate
  return @scalar.truncate if self.unitless?
  return RubyUnits::Unit.new(@scalar.truncate, @numerator, @denominator)
end

#unitless? ⇒ Boolean

returns true if no associated units false, even if the units are “unitless” like ‘radians, each, etc’

Returns:

  • (Boolean) 


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# File 'lib/ruby_units/unit.rb', line 565

def unitless?
  return(@numerator == UNITY_ARRAY && @denominator == UNITY_ARRAY)
end

#units(with_prefix = true) ⇒ String

returns the ‘unit’ part of the Unit object without the scalar

Returns:



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# File 'lib/ruby_units/unit.rb', line 1019

def units(with_prefix = true)
  return "" if @numerator == UNITY_ARRAY && @denominator == UNITY_ARRAY
  output_numerator   = []
  output_denominator = []
  num                = @numerator.clone.compact
  den                = @denominator.clone.compact

  if @numerator == UNITY_ARRAY
    output_numerator << "1"
  else
    while defn = RubyUnits::Unit.definition(num.shift) do
      if defn && defn.prefix?
        if with_prefix
          output_numerator << (defn.display_name + RubyUnits::Unit.definition(num.shift).display_name)
        end
      else
        output_numerator << defn.display_name
      end
    end
  end

  if @denominator == UNITY_ARRAY
    output_denominator = []
  else
    while defn = RubyUnits::Unit.definition(den.shift) do
      if defn && defn.prefix?
        if with_prefix
          output_denominator << (defn.display_name + RubyUnits::Unit.definition(den.shift).display_name)
        end
      else
        output_denominator << defn.display_name
      end
    end
  end

  on  = output_numerator.uniq.
      map { |x| [x, output_numerator.count(x)] }.
      map { |element, power| ("#{element}".strip + (power > 1 ? "^#{power}" : '')) }
  od  = output_denominator.uniq.
      map { |x| [x, output_denominator.count(x)] }.
      map { |element, power| ("#{element}".strip + (power > 1 ? "^#{power}" : '')) }
  out = "#{on.join('*')}#{od.empty? ? '' : '/' + od.join('*')}".strip
  return out
end

#until(time_point) ⇒ Unit

Examples:

‘min’.until(time)

Parameters:

Returns:



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# File 'lib/ruby_units/unit.rb', line 1186

def until(time_point)
  case time_point
  when Time
    return (time_point - Time.now).to_unit('s').convert_to(self)
  when DateTime, Date
    return (time_point - DateTime.now).to_unit('d').convert_to(self)
  else
    fail ArgumentError, 'Must specify a Time, Date, or DateTime'
  end
end

#zero? ⇒ Boolean

true if scalar is zero

Returns:

  • (Boolean) 


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# File 'lib/ruby_units/unit.rb', line 1145

def zero?
  return self.base_scalar.zero?
end