Raised when attempting to divide an integer by 0.

42 / 0   #=> ZeroDivisionError: divided by 0

Note that only division by an exact 0 will raise the exception:

42 /  0.0   #=> Float::INFINITY
42 / -0.0   #=> -Float::INFINITY
0  /  0.0   #=> NaN

The Comparable mixin is used by classes whose objects may be ordered. The class must define the <=> operator, which compares the receiver against another object, returning -1, 0, or +1 depending on whether the receiver is less than, equal to, or greater than the other object. If the other object is not comparable then the <=> operator should return nil. Comparable uses <=> to implement the conventional comparison operators (<, <=, ==, >=, and >) and the method between?.

class SizeMatters
  include Comparable
  attr :str
  def <=>(other)
    str.size <=> other.str.size
  end
  def initialize(str)
    @str = str
  end
  def inspect
    @str
  end
end

s1 = SizeMatters.new("Z")
s2 = SizeMatters.new("YY")
s3 = SizeMatters.new("XXX")
s4 = SizeMatters.new("WWWW")
s5 = SizeMatters.new("VVVVV")

s1 < s2                       #=> true
s4.between?(s1, s3)           #=> false
s4.between?(s3, s5)           #=> true
[ s3, s2, s5, s4, s1 ].sort   #=> [Z, YY, XXX, WWWW, VVVVV]

fileutils.rb

Copyright © 2000-2007 Minero Aoki

This program is free software. You can distribute/modify this program under the same terms of ruby.

module FileUtils

Namespace for several file utility methods for copying, moving, removing, etc.

Module Functions

require 'fileutils'

FileUtils.cd(dir, options)
FileUtils.cd(dir, options) {|dir| block }
FileUtils.pwd()
FileUtils.mkdir(dir, options)
FileUtils.mkdir(list, options)
FileUtils.mkdir_p(dir, options)
FileUtils.mkdir_p(list, options)
FileUtils.rmdir(dir, options)
FileUtils.rmdir(list, options)
FileUtils.ln(target, link, options)
FileUtils.ln(targets, dir, options)
FileUtils.ln_s(target, link, options)
FileUtils.ln_s(targets, dir, options)
FileUtils.ln_sf(target, link, options)
FileUtils.cp(src, dest, options)
FileUtils.cp(list, dir, options)
FileUtils.cp_r(src, dest, options)
FileUtils.cp_r(list, dir, options)
FileUtils.mv(src, dest, options)
FileUtils.mv(list, dir, options)
FileUtils.rm(list, options)
FileUtils.rm_r(list, options)
FileUtils.rm_rf(list, options)
FileUtils.install(src, dest, options)
FileUtils.chmod(mode, list, options)
FileUtils.chmod_R(mode, list, options)
FileUtils.chown(user, group, list, options)
FileUtils.chown_R(user, group, list, options)
FileUtils.touch(list, options)

The options parameter is a hash of options, taken from the list :force, :noop, :preserve, and :verbose. :noop means that no changes are made. The other three are obvious. Each method documents the options that it honours.

All methods that have the concept of a “source” file or directory can take either one file or a list of files in that argument. See the method documentation for examples.

There are some ‘low level’ methods, which do not accept any option:

FileUtils.copy_entry(src, dest, preserve = false, dereference = false)
FileUtils.copy_file(src, dest, preserve = false, dereference = true)
FileUtils.copy_stream(srcstream, deststream)
FileUtils.remove_entry(path, force = false)
FileUtils.remove_entry_secure(path, force = false)
FileUtils.remove_file(path, force = false)
FileUtils.compare_file(path_a, path_b)
FileUtils.compare_stream(stream_a, stream_b)
FileUtils.uptodate?(file, cmp_list)

module FileUtils::Verbose

This module has all methods of FileUtils module, but it outputs messages before acting. This equates to passing the :verbose flag to methods in FileUtils.

module FileUtils::NoWrite

This module has all methods of FileUtils module, but never changes files/directories. This equates to passing the :noop flag to methods in FileUtils.

module FileUtils::DryRun

This module has all methods of FileUtils module, but never changes files/directories. This equates to passing the :noop and :verbose flags to methods in FileUtils.

In concurrent programming, a monitor is an object or module intended to be used safely by more than one thread. The defining characteristic of a monitor is that its methods are executed with mutual exclusion. That is, at each point in time, at most one thread may be executing any of its methods. This mutual exclusion greatly simplifies reasoning about the implementation of monitors compared to reasoning about parallel code that updates a data structure.

You can read more about the general principles on the Wikipedia page for Monitors

Examples

Simple object.extend

require 'monitor.rb'

buf = []
buf.extend(MonitorMixin)
empty_cond = buf.new_cond

# consumer
Thread.start do
  loop do
    buf.synchronize do
      empty_cond.wait_while { buf.empty? }
      print buf.shift
    end
  end
end

# producer
while line = ARGF.gets
  buf.synchronize do
    buf.push(line)
    empty_cond.signal
  end
end

The consumer thread waits for the producer thread to push a line to buf while buf.empty?. The producer thread (main thread) reads a line from ARGF and pushes it into buf then calls empty_cond.signal to notify the consumer thread of new data.

Simple Class include

require 'monitor'

class SynchronizedArray < Array

  include MonitorMixin

  def initialize(*args)
    super(*args)
  end

  alias :old_shift :shift
  alias :old_unshift :unshift

  def shift(n=1)
    self.synchronize do
      self.old_shift(n)
    end
  end

  def unshift(item)
    self.synchronize do
      self.old_unshift(item)
    end
  end

  # other methods ...
end

SynchronizedArray implements an Array with synchronized access to items. This Class is implemented as subclass of Array which includes the MonitorMixin module.

Timeout long-running blocks

Synopsis

require 'timeout'
status = Timeout::timeout(5) {
  # Something that should be interrupted if it takes more than 5 seconds...
}

Description

Timeout provides a way to auto-terminate a potentially long-running operation if it hasn’t finished in a fixed amount of time.

Previous versions didn’t use a module for namespacing, however timeout is provided for backwards compatibility. You should prefer Timeout.timeout instead.

Copyright

Copyright

© 2000 Network Applied Communication Laboratory, Inc.

Copyright

© 2000 Information-technology Promotion Agency, Japan

Raised when attempting to uninstall a gem that isn’t in GEM_HOME.

Mixin methods for –version and –platform Gem::Command options.

A C union wrapper

Eigenvalues and eigenvectors of a real matrix.

Computes the eigenvalues and eigenvectors of a matrix A.

If A is diagonalizable, this provides matrices V and D such that A = V*D*V.inv, where D is the diagonal matrix with entries equal to the eigenvalues and V is formed by the eigenvectors.

If A is symmetric, then V is orthogonal and thus A = V*D*V.t

For an m-by-n matrix A with m >= n, the LU decomposition is an m-by-n unit lower triangular matrix L, an n-by-n upper triangular matrix U, and a m-by-m permutation matrix P so that L*U = P*A. If m < n, then L is m-by-m and U is m-by-n.

The LUP decomposition with pivoting always exists, even if the matrix is singular, so the constructor will never fail. The primary use of the LU decomposition is in the solution of square systems of simultaneous linear equations. This will fail if singular? returns true.

This is an abstract class. You never use this directly; it serves as a parent class for the specific declarations.

Raised to indicate that a system exit should occur with the specified exit_code

Utility methods for using the RubyGems API.

Mixin methods for security option for Gem::Commands