A class of units of physical quantities.
This class covers most functionality of UNIDATA's UDUNITS Library, however, with a more sophisticated handling of string expressions.
UDUNITS always decomposes units into the four base units and discards the original string expressions. Therefore, 'hPa' always becomes '100 kg.m-1.sec-1', and 'day' always becomes '86400 sec'. On the other hand, this library tries to keep the original expressions as much as possible by default, while allowing partial to complete decompositions if needed.
Move to the top directly of this library (where you find the file install.rb). Then, type in the following:
% ruby install.rb
Here is an example using the "irb" interactive shell ("%" is the command prompt, and ">>" is the irb prompt -- Type in those after it to test. "=>" shows the result.):
% irb --simple-prompt
>> require "numru/units"
=> true
>> un1 = NumRu::Units.new('kg.m2/s')
=> Units{kg.m2/s}
>> un2 = NumRu::Units.new('g.m')
=> Units{g.m}
>> un3 = un1 / un2
=> Units[Multi[Pow[Name[g], Number[-1]], Name[kg], Pow[Name[m], Number[1]], Pow[Name[s], Number[-1]]]]
>> un1.to_s
=> "kg.m2/s"
>> un2.to_s
=> "g.m"
>> un3.to_s
=> "g-1 kg.m1 s-1"
>> un3.reduce5
=> Units[Multi[Number[1000], Pow[Name[m], Number[1]], Pow[Name[s], Number[-1]]]]
>> un3.to_s
=> "1000 m1 s-1"
Note the difference between the results of un3.to_s before and after un3.reduce5, where the former retains the literal expression of each atomic unit, while the latter does the maximum reduction. You can change the default behavior by using the class method reduce_level=:
>> NumRu::Units.reduce_level = 5 => :reduce5 >> un3.to_s => "1000 m1 s-1"
Note that you can eliminate the prefix NumRu:: by "including" it:
>> require "numru/units"
=> true
>> include NumRu
=> Object
>> un1 = Units.new('kg.m2/s')
=> Units{kg.m2/s}
>> Units.reduce_level = 5
=> :reduce5
In what follows, the prefix NumRu:: is omitted for conciseness. See Usage Examples on this issue.
Units.new(string)Constructor.
ARGUMENTS
RETURN VALUE
EXAMPLE
units = Units.new('kg.m2/s')
units = Units.new('100 m')
units = Units.new('g/kg')
units = Units.new('hour since 2003-10-01 00:00:0 +0:00')
units = Units.new('hour since 2003-10-01') # same as above
units = Units.new('minutes since 2003-10-01 03:15:22.5 -6:00')Units[string]Units.reduce_level=(n)Set the reduction level before to_s is applied.
ARGUMENTS
to_s*(other)Multiplies self with another units. Applies reduce4 to format the string expression of the result.
ARGUMENTS
RETURN VALUE
/(other)Divides self with another units. Applies reduce4 to format the string expression of the result.
ARGUMENTS
RETURN VALUE
**(pow)Power. Applies reduce4 to format the string expression of the result.
ARGUMENTS
RETURN VALUE
==(other)===(other)=~(other)reduce4Moderately reduces the string expression of the units (destructive method). This method preserves string expression of atomic units. See also reduce5.
RETURN VALUE
EXAMPLE
Untis.new('hour/hour').reduce4.to_s
# => "1"
Units.new('mm/m').reduce4.to_s
# => "mm.m-1"reduce5Aggressively reduces the string expression of the units (destructive method). See also reduce4.
RETURN VALUE
EXAMPLE
Units.new('hour/hour').reduce4.to_s
# => "1"
Units.new('mm/m').reduce5.to_s
# => "0.001"convert(numeric, to_units)Converts a numeric of the current units (=self) to to_units.
ARGUMENTS
RETURN VALUE
EXCEPTIONS
convert2(val, to_units)Like convert, but (1) accpets any Numeric-like objects, and (2) does not raise an exception even if the two units are incompatible -- in this case, simply returns val (warned).
ARGUMENTS
RETURN VALUE
factor_and_offset(to_units)Returns the factor and offset to convert from self to to_units. The conversion is done as scale_factor * operand + add_offset.
ARGUMENTS
RETURN VALUE
EXAMPLE
scale_factor, add_offset = from_units.factor_and_offset(to_units) to = scale_factor * from + add_offset