Class: 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_REGEX = 
/(\d+)\s*(?:'|ft|feet)\s*(\d+)\s*(?:"|in|inches)/
TIME_REGEX = 
/(\d+)*:(\d+)*:*(\d+)*[:,]*(\d+)*/
LBS_OZ_REGEX = 
/(\d+)\s*(?:#|lbs|pounds|pound-mass)+[\s,]*(\d+)\s*(?:oz|ounces)/
SCI_NUMBER = 
%r{([+-]?\d*[.]?\d+(?:[Ee][+-]?)?\d*)}
RATIONAL_NUMBER = 
/\(?([+-]?\d+)\/(\d+)\)?/
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+)/
UNCERTAIN_REGEX = 
/#{SCI_NUMBER}\s*\+\/-\s*#{SCI_NUMBER}\s(.+)/
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,
:memory,
: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        =>  :resistance,
312078        =>  :capacitance,
3199980       =>  :activity,
3199997       =>  :molar_concentration,
3200000       =>  :substance,
63999998      =>  :illuminance,
64000000      =>  :luminous_power,
1280000000    =>  :currency,
25600000000   =>  :memory,
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 310

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 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 = Unit.parse_into_numbers_and_units(options[0])
    unless @@cached_units.keys.include?(opt_units) || (opt_units =~ /(#{Unit.temp_regex})|(pounds|lbs[ ,]\d+ ounces|oz)|('\d+")|(ft|feet[ ,]\d+ in|inch|inches)|%|(#{TIME_REGEX})|i\s?(.+)?|&plusmn;|\+\/-/)
      @@cached_units[opt_units] = (self.scalar == 1 ? self : opt_units.unit) if opt_units && !opt_units.empty?
    end
  end
  unless @@cached_units.keys.include?(unary_unit) || (unary_unit =~ /#{Unit.temp_regex}/) then
    @@cached_units[unary_unit] = (self.scalar == 1 ? self : unary_unit.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 236

def base_denominator
  @base_denominator
end

#base_numerator ⇒ Array

Returns:



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# File 'lib/ruby_units/unit.rb', line 233

def base_numerator
  @base_numerator
end

#base_scalar ⇒ Numeric

Returns:



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# File 'lib/ruby_units/unit.rb', line 230

def base_scalar
  @base_scalar
end

#denominator ⇒ Array

Returns:



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# File 'lib/ruby_units/unit.rb', line 224

def denominator
  @denominator
end

#numerator ⇒ Array

Returns:



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# File 'lib/ruby_units/unit.rb', line 221

def numerator
  @numerator
end

#output ⇒ String

Returns:



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# File 'lib/ruby_units/unit.rb', line 239

def output
  @output
end

#scalar ⇒ Numeric

Returns:



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# File 'lib/ruby_units/unit.rb', line 218

def scalar
  @scalar
end

#signature ⇒ Integer

Returns:

  • (Integer) 


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# File 'lib/ruby_units/unit.rb', line 227

def signature
  @signature
end

#unit_name ⇒ String

Returns:



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# File 'lib/ruby_units/unit.rb', line 242

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 407

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 392

def self.cached
  return @@cached_units
end

.clear_cache ⇒ true

Returns:

  • (true) 


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# File 'lib/ruby_units/unit.rb', line 398

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

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

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

Examples:

Block form

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

Unit::Definition form

unit_definition = Unit::Definition.new("foobar") {|foobar| foobar.definition = Unit("1 baz")}
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 184

def self.define(unit_definition, &block)
  if block_given?
    raise ArgumentError, "When using the block form of Unit.define, pass the name of the unit" unless unit_definition.instance_of?(String)
    unit_definition = Unit::Definition.new(unit_definition, &block)
  end
  Unit.definitions[unit_definition.name] = unit_definition
  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 152

def self.defined?(unit)
  return @@UNIT_VALUES.keys.include?("<#{unit}>")
end

.definition(_unit) ⇒ Unit::Definition?

return the unit definition for a unit

Parameters:

Returns:



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# File 'lib/ruby_units/unit.rb', line 159

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 166

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 415

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

.redefine!(name, &block) {|Unit::Definition| ... } ⇒ 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 200

def self.redefine!(name, &block)
  raise ArgumentError, "A block is required to redefine a unit" unless block_given?
  unit_definition = self.definition(name)
  yield unit_definition
  self.define(unit_definition)
end

.setup ⇒ true

setup internal arrays and hashes

Returns:

  • (true) 


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# File 'lib/ruby_units/unit.rb', line 130

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

  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 210

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

Returns:

  • (Integer) 


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

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 764

def *(other)
  case other
  when Unit
    raise ArgumentError, "Cannot multiply by temperatures" if [other,self].any? {|x| x.is_temperature?}
    opts = Unit.eliminate_terms(@scalar*other.scalar, @numerator + other.numerator ,@denominator + other.denominator)
    opts.merge!(:signature => @signature + other.signature)
    return Unit.new(opts)
  when Numeric
    return 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 837

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:

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 696

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?
          Unit.new(:scalar => (self.scalar + other.convert_to(self.temperature_scale).scalar), :numerator => @numerator, :denominator=>@denominator, :signature => @signature)
        else
          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.unit.to_base.scalar))
        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 731

def -(other)
  case other
    when Unit
      case
      when self.zero?
        -other.dup
      when self =~ other
        case
          when [self, other].all? {|x| x.is_temperature?}
            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?
            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.unit.scalar/self.units.unit.to_base.scalar))
            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 1080

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 785

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 = Unit.eliminate_terms(@scalar/other.scalar, @numerator + other.denominator ,@denominator + other.numerator)
    opts.merge!(:signature=> @signature - other.signature)
    return Unit.new(opts)
  when Numeric
    raise ZeroDivisionError if other.zero?
    return 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:

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 597

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.zero?
    return self.base_scalar <=> 0
  when other.instance_of?(Unit)
    raise ArgumentError, "Incompatible Units (#{self.units} !~ #{other.units})" unless self =~ other
    return self.base_scalar <=> other.base_scalar
  else
    x,y = coerce(other)
    return x <=> y
  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:

Returns:

  • (Boolean) 


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# File 'lib/ruby_units/unit.rb', line 622

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:

Unit("100 cm") === Unit("100 cm")   # => true
Unit("100 cm") === Unit("1 m")      # => false

Parameters:

Returns:

  • (Boolean) 


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# File 'lib/ruby_units/unit.rb', line 671

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:

Returns:

  • (Boolean) 


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# File 'lib/ruby_units/unit.rb', line 648

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 1087

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

#ago ⇒ Unit

Examples:

‘5 min’.unit.ago

Returns:



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# File 'lib/ruby_units/unit.rb', line 1163

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 1029

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 1169

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

#ceil ⇒ Numeric, Unit

ceil of a unit

Returns:



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# File 'lib/ruby_units/unit.rb', line 1094

def ceil
  return @scalar.ceil if self.unitless?
  return 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 1227

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

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 939

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 Unit.new("#{q} #{target_unit}")
  else
    case other
    when Unit
      return self if other.units == self.units
      target = other
    when String
      target = Unit.new(other)
    else
      raise ArgumentError, "Unknown target units"
    end
    raise ArgumentError,  "Incompatible Units" 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 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 defintion from

Returns:



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# File 'lib/ruby_units/unit.rb', line 254

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:

Returns:

Raises:

  • (ArgumentError) 


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# File 'lib/ruby_units/unit.rb', line 807

def divmod(other)
  raise ArgumentError, "Incompatible Units" 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 1100

def floor
  return @scalar.floor if self.unitless?
  return 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 1212

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(option = 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 556

def inspect(option=nil)
  return super() if option == :dump
  return self.to_s
end

#inverse ⇒ Unit

returns inverse of Unit (1/unit)

Returns:



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# File 'lib/ruby_units/unit.rb', line 916

def inverse
  return Unit("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 428

def is_base?
  return @is_base if defined? @is_base
  @is_base = (@numerator + @denominator).compact.uniq.
                                          map {|unit| 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 571

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 564

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 386

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 247

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 866

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’.unit.pred #=> ‘1 mm’.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 1131

def pred
  raise ArgumentError, "Non Integer Scalar" unless @scalar == @scalar.to_i
  return 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 886

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 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 1106

def round(ndigits = 0)
  return @scalar.round(ndigits) if self.unitless?
  return 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 1183

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

#succ ⇒ Unit Also known as: next

returns next unit in a range. ‘1 mm’.unit.succ #=> ‘2 mm’.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 1121

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

#temperature_scale ⇒ String

returns the ‘degree’ unit associated with a temperature unit

Examples:

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

Returns:

  • (String) —

    possible values: degC, degF, degR, or degK



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# File 'lib/ruby_units/unit.rb', line 579

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 441

def to_base
  return self if self.is_base?
  if @@UNIT_MAP[self.units] =~ /\A<(?:temp|deg)[CRF]>\Z/
    if RUBY_VERSION < "1.9"
      # :nocov_19:
      @signature = @@KINDS.index(:temperature)
      # :nocov_19:
    else
      #:nocov:
      @signature = @@KINDS.key(:temperature)
      #:nocov:
    end
    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= Unit.new(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 1005

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 1151

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 1146

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 997

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 1013

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 1022

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 511

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
      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
        "#{@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 1138

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 421

def to_unit
  self
end

#to_yaml(opts = {}) ⇒ String

basically a copy of the basic to_yaml. Needed because otherwise it ends up coercing the object to a string before YAML’izing it.

Parameters:

  • opts (Hash) (defaults to: {})

Returns:



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# File 'lib/ruby_units/unit.rb', line 278

def to_yaml( opts = {} )
  YAML::quick_emit( object_id, opts ) do |out|
    out.map( taguri, to_yaml_style ) do |map|
      for m in to_yaml_properties do
        map.add( m[1..-1], instance_variable_get( m ) )
      end
    end
  end
end

#to_yaml_properties ⇒ Array

a list of properties to emit to yaml

Returns:



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# File 'lib/ruby_units/unit.rb', line 270

def to_yaml_properties
  %w{@scalar @numerator @denominator @signature @base_scalar}
end

#truncate ⇒ Numeric, Unit

Returns:



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# File 'lib/ruby_units/unit.rb', line 1112

def truncate
  return @scalar.truncate if self.unitless?
  return 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 587

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

#units ⇒ String

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

Returns:



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# File 'lib/ruby_units/unit.rb', line 1035

def units
  return "" if @numerator == UNITY_ARRAY && @denominator == UNITY_ARRAY
  return @unit_name unless @unit_name.nil?
  output_numerator   = []
  output_denominator = []
  num                = @numerator.clone.compact
  den                = @denominator.clone.compact

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

  if @denominator == UNITY_ARRAY
    output_denominator = []
  else
    while defn = Unit.definition(den.shift) do
      if defn && defn.prefix?
        output_denominator << defn.display_name + Unit.definition(den.shift).display_name
      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
  @unit_name = out unless self.kind == :temperature
  return out
end

#until(time_point) ⇒ Unit

Examples:

‘min’.until(time)

Parameters:

Returns:



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# File 'lib/ruby_units/unit.rb', line 1197

def until(time_point)
  case time_point
  when Time
    return (time_point - Time.now).unit('s').convert_to(self)
  when DateTime, Date
    return (time_point - DateTime.now).unit('d').convert_to(self)
  else
    raise 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 1157

def zero?
  return self.base_scalar.zero?
end