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class Bignum
Parent: Integer
Version: 1.6

Index:

Arithmetic operations Bit operations <=> [ ] size to_f to_i to_s

Bignum objects hold integers outside the range of Fixnum. Bignum objects are created automatically when integer calculations would otherwise overflow a Fixnum. When a calculation involving Bignum objects returns a result that will fit in a Fixnum, the result is automatically converted.

For the purposes of the bitwise operations and [], a Bignum is treated as if it were an infinite-length bitstring with 2's complement representation.

While Fixnum values are immediate, Bignum objects are not-assignment and parameter passing work with references to objects, not the objects themselves.

instance methods
Arithmetic operations
Performs various arithmetic operations on big.{:0021:}:0021:

big + aNumeric Addition
big - aNumeric Subtraction
big * aNumeric Multiplication
big / aNumeric Division
big % aNumeric Modulo
big ** aNumeric Exponentiation
Bit operations
Performs various operations on the binary representations of the Bignum. 

~ big Invert bits
big | aNumeric Bitwise OR
big & aNumeric Bitwise AND
big ^ aNumeric Bitwise EXCLUSIVE OR
big << aNumeric Left-shift aNumeric bits
big >> aNumeric Right-shift aNumeric bits (with sign extension)
<=> big <=> aNumeric -> -1, 0, +1
Comparison-Returns -1, 0, or +1 depending on whether big is less than, equal to, or greater than aNumeric. This is the basis for the tests in Comparable.
[ ] big[ n ] -> 0, 1
Bit Reference-Returns the nth bit in the (assumed) binary representation of big, where big[0] is the least significant bit. 

a = 9**15
50.downto(0) do |n|
  print a[n]
end

produces: 

000101110110100000111000011110010100111100010111001

size big.size -> anInteger
Returns the number of bytes in the machine representation of big.

(256**10 - 1).size -> 10
(256**20 - 1).size -> 20
(256**40 - 1).size -> 40

to_f big.to_f -> aFloat
Converts big to a Float. If big doesn't fit in a Float, the result is infinity.
to_i big.to_i -> big
Returns big.
to_s big.to_s -> aString
Returns a string containing the decimal representation of big.

Extracted from the book "Programming Ruby - The Pragmatic Programmer's Guide"
Copyright © 2000 Addison Wesley Longman, Inc. Released under the terms of the Open Publication License V1.0.
This reference is available for download.