Class: Eymiha::UnitsHash

Inherits:
Hash
  • Object
show all
Defined in:
lib/eymiha/units/units_hash.rb

Overview

The unit part of a NumericWithUnits is a UnitsHash - a Hash from UnitsUnit instances to powers.

Constant Summary collapse

@@debug = 
false

Class Method Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(unit = nil, power = 1) ⇒ UnitsHash

:nodoc



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

def initialize(unit = nil,power = 1) # :nodoc
  if unit
    if unit.kind_of? UnitsUnit
      self[unit] = power
    elsif unit.kind_of? UnitsHash
      unit.each { |k,v| self[k] = v*power }
    else
      raise UnitsException.new("invalid unit: #{unit}")
    end
  end
end

Class Method Details

.debug=(value) ⇒ Object 



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

def self.debug=(value)
  @@debug = value
end

Instance Method Details

#**(power) ⇒ Object

Returns a new UnitsHash whose value is the instance raised to the given power.



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

def **(power)
  clone.power!(power)
end

#abbrevs_to_s ⇒ Object

:nodoc:



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# File 'lib/eymiha/units/units_hash.rb', line 41

def abbrevs_to_s # :nodoc:
  p = select {|k,v| v > 0}.sort{|e1,e2| e1[1] <=> e2[1]}.collect {|e|
    "#{e[0].abbrevs[0] || e[0].name}#{(e[1] == 1) ? "" : "^#{e[1]}"}"}
  n = select {|k,v| v < 0}.sort{|e1,e2| e1[1] <=> e2[1]}.collect {|e|
    "#{e[0].abbrevs[0] || e[0].name}#{(e[1] == -1) ? "" : "^#{-e[1]}"}"}
  numerator = (p.size > 0)? p.join(" ") : (n.size > 0)? "1" : ""
  denominator = (n.size > 0)? ((p.size > 0)? " / " : "/")+n.join(" ") : ""
  "#{numerator}#{denominator}"
end

#derived? ⇒ Boolean

Returns true is any of the instance’s components are derived.

Returns:

  • (Boolean) 


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# File 'lib/eymiha/units/units_hash.rb', line 90

def derived?
  keys.select{|unit|
    unit.units_system.units_measure.derived != nil}.size > 0
end

#has_units? ⇒ Boolean

Return true if the instance is not equal to 1, ie. has at least one non-zero exponent.

Returns:

  • (Boolean) 


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# File 'lib/eymiha/units/units_hash.rb', line 112

def has_units?
  (self.select {|k,v| v != 0.0}).size > 0
end

#measure ⇒ Object

Returns the UnitsMeasure of the instance if defined.



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# File 'lib/eymiha/units/units_hash.rb', line 82

def measure
  measure = UnitsMeasure.new
  each { |unit,power|
    measure.merge_derivation unit.units_system.units_measure => power }
  Units.find_by_derivation(measure.derived)
end

#merge(value, power = 1) ⇒ Object Also known as: *

Returns a new UnitsHash whose value is the instance’s units and powers have been merged with the given value raised to the power.



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# File 'lib/eymiha/units/units_hash.rb', line 65

def merge(value,power=1)
  clone.merge!(value,power)
end

#merge!(value, power = 1) ⇒ Object

Merges and returns the instance after the value raised to the power has been merged into it.



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# File 'lib/eymiha/units/units_hash.rb', line 71

def merge!(value,power=1)
  value.unit.each { |k,v|
    self[k] = (self[k] || 0) + v*power
    delete k if self[k] == 0
  }
  self
end

#power!(power) ⇒ Object

Raises and returns the instance after each of its exponents has been raised by the given power.



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# File 'lib/eymiha/units/units_hash.rb', line 53

def power!(power)
  self.each { |k,v| self[k] = v*power }
end

#reduce ⇒ Object

Return a NumericWithUnits that represents the instance when all derived units have been replaced with the units from which they derive.



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# File 'lib/eymiha/units/units_hash.rb', line 97

def reduce
  puts "UnitsHash:reduce #{to_s}" if @@debug
  factor = 1.0
  new_unit = UnitsHash.new
  each do |unit,power|
    puts "  #{unit} #{power}" if @@debug
    factor *= unit.equals.numeric**power
    puts "  #{factor}" if @@debug
    new_unit.merge!(unit.equals,power)
  end
  factor.unite new_unit
end

#to_s(numeric = 1, use_abbrevs = false) ⇒ Object

Returns a String reprentation of the instance. If there is only one item in the UnitsHash, whole names are rendered; otherwise abbreviations are used.



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# File 'lib/eymiha/units/units_hash.rb', line 30

def to_s(numeric = 1,use_abbrevs = false)
  if size == 1 &&
      (su = select {|k,v| v == 1}).size == 1 &&
      !use_abbrevs
    su = su.to_a[0][0]
    ((numeric == 1)? su.name : su.plural).gsub(/_/,' ')
  else
    abbrevs_to_s
  end
end