A Brief List of Less Used Libraries


Calculates the set of unambiguous abbreviations for a given set of strings.

require 'abbrev'
require 'pp'

pp Abbrev.abbrev(['ruby'])
#=>  {"ruby"=>"ruby", "rub"=>"ruby", "ru"=>"ruby", "r"=>"ruby"}

pp Abbrev.abbrev(%w{ ruby rules })


{ "ruby"  =>  "ruby",
  "rub"   =>  "ruby",
  "rules" =>  "rules",
  "rule"  =>  "rules",
  "rul"   =>  "rules" }

It also provides an array core extension, Array#abbrev.

pp %w{ summer winter }.abbrev


{ "summer"  => "summer",
  "summe"   => "summer",
  "summ"    => "summer",
  "sum"     => "summer",
  "su"      => "summer",
  "s"       => "summer",
  "winter"  => "winter",
  "winte"   => "winter",
  "wint"    => "winter",
  "win"     => "winter",
  "wi"      => "winter",
  "w"       => "winter" }

Abbrev Reference


CMath is a library that provides trigonometric and transcendental functions for complex numbers. The functions in this module accept integers, floating-point numbers or complex numbers as arguments.

Note that the selection of functions is similar, but not identical, to that in module math. The reason for having two modules is that some users aren’t interested in complex numbers, and perhaps don’t even know what they are. They would rather have Math.sqrt(-1) raise an exception than return a complex number.

For more information you can see Complex class.

CMath Reference


The GetoptLong class allows you to parse command line options similarly to the GNU getopt_long() C library call. Note, however, that GetoptLong is a pure Ruby implementation.

GetoptLong allows for POSIX-style options like --file as well as single letter options like -f

The empty option -- (two minus symbols) is used to end option processing. This can be particularly important if options have optional arguments.

Here is a simple example of usage:

require 'getoptlong'

opts = GetoptLong.new(
  [ '--help', '-h', GetoptLong::NO_ARGUMENT ],
  [ '--repeat', '-n', GetoptLong::REQUIRED_ARGUMENT ],
  [ '--name', GetoptLong::OPTIONAL_ARGUMENT ]

dir = nil
name = nil
repetitions = 1
opts.each do |opt, arg|
  case opt
    when '--help'
      puts <<-EOF
hello [OPTION] ... DIR

-h, --help:
   show help

--repeat x, -n x:
   repeat x times

--name [name]:
   greet user by name, if name not supplied default is John

DIR: The directory in which to issue the greeting.
    when '--repeat'
      repetitions = arg.to_i
    when '--name'
      if arg == ''
        name = 'John'
        name = arg

if ARGV.length != 1
  puts "Missing dir argument (try --help)"
  exit 0

dir = ARGV.shift

for i in (1..repetitions)
  print "Hello"
  if name
    print ", #{name}"

Example command line:

hello -n 6 --name -- /tmp

GetoptLong Reference


Helper module for easily defining exceptions with predefined messages.

Exception2MessageMapper Reference


NKF - Ruby extension for Network Kanji Filter

NKF Reference


PStore implements a file based persistence mechanism based on a Hash. User code can store hierarchies of Ruby objects (values) into the data store file by name (keys). An object hierarchy may be just a single object. User code may later read values back from the data store or even update data, as needed.

The transactional behavior ensures that any changes succeed or fail together. This can be used to ensure that the data store is not left in a transitory state, where some values were updated but others were not.

Behind the scenes, Ruby objects are stored to the data store file with Marshal. That carries the usual limitations. Proc objects cannot be marshalled, for example.

PStore Reference


A module to implement the Linda distributed computing paradigm in Ruby.

Rinda is part of DRb (dRuby).

Rinda Reference


This class watches for termination of multiple threads. Basic functionality (wait until specified threads have terminated) can be accessed through the class method ThreadsWait::all_waits. Finer control can be gained using instance methods.


ThreadsWait.all_waits(thr1, thr2, ...) do |t|
  STDERR.puts "Thread #{t} has terminated."

th = ThreadsWait.new(thread1,...)
th.next_wait # next one to be done

ThreadsWait Reference


TSort implements topological sorting using Tarjan’s algorithm for strongly connected components.

TSort is designed to be able to be used with any object which can be interpreted as a directed graph.

TSort requires two methods to interpret an object as a graph, tsort_each_node and tsort_each_child.

  • tsort_each_node is used to iterate for all nodes over a graph.
  • tsort_each_child is used to iterate for child nodes of a given node.

The equality of nodes are defined by eql? and hash since TSort uses Hash internally.

TSort Reference


Weak Reference class that allows a referenced object to be garbage-collected.

A WeakRef may be used exactly like the object it references.


foo = Object.new            # create a new object instance
p foo.to_s                  # original's class
foo = WeakRef.new(foo)      # reassign foo with WeakRef instance
p foo.to_s                  # should be same class
GC.start                    # start the garbage collector
p foo.to_s                  # should raise exception (recycled)

WeakRef Reference