UOM: Unit of Measure library

Git: http://github.com/caruby/uom
Author: OHSU Knight Cancer Institute
Copyright: 2010, 2011
License: MIT License

Synopsis

UOM implements Units of Measurement based on the International System of Units (SI). The base SI units, metric scalar factors and all possible combinations of these units are supported out of the box. Common alternative non-metric measurement systems, e.g. US Customary units, are supported with conversions between these units and the SI units. Supported units are listed in +doc/units.txt+.

Additional units can be defined with conversion to an existing unit. UOM infers full conversion capability between units of the same dimension from the minimal number of conversion definitions. See the Usage section for an example of combining pre-defined units into a novel unit.

Arithmetic operations between UOM Measurement objects converts the measurement units and scalar factors as necessary, including unit products, quotients and powers of arbitrary complexity.

Feature List

Built-in support for standard scientific units
Conversion between arbitrary unit combinations
Custom unit definition
Measurement parser

Installing

To install UOM, use the following command:

$ gem install caruby-uom

(Add sudo if you're installing under a POSIX system as root)

Alternatively, if you've checked the source out directly, you can call rake install from the root project directory.

Usage

Create a Measurement

require 'uom'

UOM::Measurement.new(:g, 1) #=> 1 gram
UOM::Measurement.new(:mg, 1) #=> 1 milligram
UOM::Measurement.new(:mg_per_l, 1) #=> 1 milligram per liter

Scale a Measurement

UOM::Measurement.new(:g, 1).as(:mg) #=> 1000 milligrams

Measurement arithmetic

UOM::Measurement.new(:g, 1) * 2 #=> 2 grams
UOM::Measurement.new(:g, 2) / UOM::Measurement.new(:l, 1) #=> 2 milligrams per liter

Parse a measurement String

"1 g".to_measurement #=> 1 gram Measurement
"1 gm".to_measurement #=> 1 gram Measurement
"2 grams".to_measurement #=> 2 gram Measurement

Convert a Measurement

UOM::Measurement.new(:g, 2).to_f #=> 2.0
UOM::Measurement.new(:g, 1).to_s #=> "1 gram"
UOM::Measurement.new(:g, 2).to_s #=> "2 grams"

Label a novel unit

module UOM
  # joule-pecks per erg-gauss
  JPEG = Unit.for((JOULE * PECK) / (ERG * GAUSS)).add_abbreviation(:jpeg)
end
UOM::Measurement.new(:jpeg, 1) #=> 1 jpeg