class Integer
Constants
- BASE_DIGITS
Cached constants for encoding numbers into bases up to 64
- SMALL_POWERS_OF_2
Public Instance Methods
'true' if the integer is 0
# File lib/epitools/core_ext/truthiness.rb, line 61 def blank?; self == 0; end
Factorial
# File lib/epitools/core_ext/numbers.rb, line 368 def fact if self < 0 -(1..-self).reduce(:*) elsif self == 0 1 else (1..self).reduce(:*) end end
Returns the all the prime factors of a number.
# File lib/epitools/core_ext/numbers.rb, line 360 def factors Prime # autoload the prime module prime_division.map { |n,count| [n]*count }.flatten end
Fibonacci (recursive style)
# File lib/epitools/core_ext/numbers.rb, line 382 def fib self < 2 ? self : (self-1).fib + (self-2).fib end
# File lib/epitools/core_ext/truthiness.rb, line 63 def integer?; true; end
Flip all bits except the sign bit.
NOTE: This method should only be used with unsigned integers; if you use it with a signed integer, it will only flip the non-sign bits (I dunno if that's useful for anything; nothing comes to mind.)
# File lib/epitools/core_ext/numbers.rb, line 394 def invert to_s(2).tr("01","10").to_i(2) end
Am I a prime number?
# File lib/epitools/core_ext/numbers.rb, line 337 def prime? Prime.prime? self end
Return a specified number of primes (optionally starting at the argument)
# File lib/epitools/core_ext/numbers.rb, line 344 def primes(starting_at=2) result = [] current = starting_at loop do if current.prime? result << current return result if result.size >= self end current += 1 end end
Convert a number into a string representation (encoded in a base <= 64).
The number is represented usiing the characters: 0..9, A..Z, a..z, _, -
(Setting base to 64 results in the encoding scheme that YouTube and url shorteners use for their ID strings, eg: www.youtube.com/watch?v=dQw4w9WgXcQ)
# File lib/epitools/core_ext/numbers.rb, line 300 def to_base(base=10) raise "Error: Can't handle bases greater than 64" if base > 64 n = self digits = [] alphabet = BASE_DIGITS[0...base] if bits = SMALL_POWERS_OF_2[base] # a slightly accelerated version for powers of 2 mask = (2**bits)-1 loop do digits << (n & mask) n = n >> bits break if n == 0 end else # generic base conversion loop do n, digit = n.divmod(base) digits << digit break if n == 0 end end digits.reverse.map { |d| alphabet[d] }.join end
# File lib/epitools/core_ext/numbers.rb, line 330 def to_base62 to_base(62) end
Convert the number to an array of bits (least significant digit first, or little-endian).
# File lib/epitools/core_ext/numbers.rb, line 280 def to_bits # TODO: Why does this go into an infinite loop in 1.8.7? ("%b" % self).chars.to_a.reverse.map(&:to_i) end
Convert the number into a hexadecimal string representation. (Identical to to_s(16), except that numbers < 16 will have a 0 in front of them.)
# File lib/epitools/core_ext/numbers.rb, line 273 def to_hex "%0.2x" % self end