Class: Integer

Inherits:
Object show all
Includes:
Nuggets::Integer::LengthMixin
Defined in:
lib/nuggets/integer/factorial.rb,
lib/nuggets/integer/length.rb,
lib/nuggets/integer/to_binary_s.rb,
lib/nuggets/util/dotted_decimal.rb

Overview

–

#

A component of ruby-nuggets, some extensions to the Ruby programming # language. #

#

Copyright © 2007-2008 Jens Wille #

#

Authors: #

Jens Wille <jens.wille@uni-koeln.de>                                    #
                                                                        #

ruby-nuggets is free software; you can redistribute it and/or modify it # under the terms of the GNU General Public License as published by the Free # Software Foundation; either version 3 of the License, or (at your option) # any later version. #

#

ruby-nuggets is distributed in the hope that it will be useful, but WITHOUT # ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or # FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for # more details. #

#

You should have received a copy of the GNU General Public License along # with ruby-nuggets. If not, see <www.gnu.org/licenses/>. #

#

++

Constant Summary collapse

FACTORIAL =

Memoization container: integer => factorial(integer)

{ 0 => 1 }

Instance Method Summary collapse

Methods included from Nuggets::Integer::LengthMixin

#digit_count, #length

Instance Method Details

#factorial ⇒ Object Also known as: fac, f!

call-seq:

int.factorial => anInteger

Calculate the factorial of int. To use the memoized version: Integer.send(:alias_method, :factorial, :factorial_memoized)



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# File 'lib/nuggets/integer/factorial.rb', line 38

def factorial
  (1..self).inject { |f, i| f * i }
end

#factorial_memoized ⇒ Object

call-seq:

int.factorial_memoized => anInteger

Calculate the factorial of int with the help of memoization (Which gives a considerable speedup for repeated calculations – at the cost of memory).

WARNING: Don’t try to calculate the factorial this way for “large” integers! This might well bring your system down to its knees… ;-)



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# File 'lib/nuggets/integer/factorial.rb', line 50

def factorial_memoized
  FACTORIAL[self] ||= (1..self).inject { |f, i| FACTORIAL[i] ||= f * i }
end

#to_binary_s(length = nil) ⇒ Object

call-seq:

int.to_binary_s => aString
int.to_binary_s(length) => aString

Returns int as binary number string; optionally zero-padded to length.



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# File 'lib/nuggets/integer/to_binary_s.rb', line 35

def to_binary_s(length = nil)
  "%0#{length}d" % to_s(2)
end

#to_dotted_decimal ⇒ Object

call-seq:

int.to_dotted_decimal => aString

Converts int to dotted-decimal notation.



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# File 'lib/nuggets/util/dotted_decimal.rb', line 36

def to_dotted_decimal
  to_binary_s(32).unpack('a8' * 4).map { |s| s.to_i(2) }.join('.')
end