Class: Eymiha::UnitsMeasure

Inherits:
MethodicHash
  • Object
show all
Defined in:
lib/eymiha/units/units_measure.rb

Overview

A UnitsMeasure groups sets of units that measure the same quality.

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize ⇒ UnitsMeasure

:nodoc:



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# File 'lib/eymiha/units/units_measure.rb', line 17

def initialize # :nodoc:
  @formats = MethodicHash.new
end

Instance Attribute Details

#derived ⇒ Object

A Hash of UnitsMeasures to powers that represent the bases for this UnitsMeasure if it is derived.



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# File 'lib/eymiha/units/units_measure.rb', line 11

def derived
  @derived
end

#formats ⇒ Object (readonly)

A Methodic Hash mapping names of formats to procs that implement them.



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# File 'lib/eymiha/units/units_measure.rb', line 15

def formats
  @formats
end

Instance Method Details

#*(factor) ⇒ Object

Returns a new UnitsMeasure equal to the instance multiplied by another UnitsMeasure. This is typically used to derive UnitsMeasures - for example, if length is a UnitsMeasure, then length*length could be used as the target to derive area.



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# File 'lib/eymiha/units/units_measure.rb', line 59

def *(factor)
  UnitsMeasure.new.merge_derivation(self).merge_derivation(factor)
end

#**(exponent) ⇒ Object

Returns a new UnitsMeasure equal to the instance raised to the given power. This is typically used to derive UnitsMeasures - for example, if length is a UnitsMeasure, then length**3 could be used as the target to derive volume.



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# File 'lib/eymiha/units/units_measure.rb', line 43

def **(exponent)
  UnitsMeasure.new.merge_derivation(self => exponent)
end

#/(divisor) ⇒ Object

Returns a new UnitsMeasure equal to the instance divided by another UnitsMeasure. This is typically used to derive UnitsMeasures - for example, if mass and volume are UnitsMeasures, then mass/volume could be used as the target to derive density.



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# File 'lib/eymiha/units/units_measure.rb', line 51

def /(divisor)
  UnitsMeasure.new.merge_derivation(self).merge_derivation(divisor,-1)
end

#format(options) ⇒ Object

Associates the name of a format with an output formatter.



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# File 'lib/eymiha/units/units_measure.rb', line 89

def format(options)
  @formats[options[:name]] = options[:format]
end

#merge_derivation(derivation, multiplier = 1) ⇒ Object

:nodoc:



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# File 'lib/eymiha/units/units_measure.rb', line 63

def merge_derivation derivation, multiplier=1 # :nodoc:
  current = (self.derived ||= {})
  if derivation.kind_of? UnitsMeasure
    if derivation.derived
      derivation.derived.each {|key,value|
        current[key] = (current[key] || 0) + multiplier*value } 
    else
      current[derivation] = (current[derivation] || 0) + multiplier
    end
  elsif derivation.kind_of? Hash
    derivation.each {|key,value|
      current[key] = ((current[key] || 0 ) + multiplier*value) }
  else
    raise UnitsException,
         "Cannot add #{derivation.class_name} to derivation"
  end
  self
end

#names ⇒ Object

Returns the names by which this UnitsMeasure is known.



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# File 'lib/eymiha/units/units_measure.rb', line 35

def names
  Units.names_of self
end

#system(name, &block) ⇒ Object

Defines or extends a UnitsSystem. During definition, if forward references between entities may occur and when encountered, are stored. Upon completion of the definition, if any existing unresolved still exist, an attempt is made to resolve them.



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# File 'lib/eymiha/units/units_measure.rb', line 25

def system(name,&block)
  Units.defining self
  system = (self[name] ||= UnitsSystem.new(self,name))
  block.call system if block_given?
  Units.resolve_forward_references
  Units.defining nil
  system
end

#to_s ⇒ Object

Returns a String containing the names of this UnitsMeasure and the namse of the UnitsSystems defined within it.



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# File 'lib/eymiha/units/units_measure.rb', line 84

def to_s
  "#{class_name} #{names} #{keys}"
end