Class: Integer
- Defined in:
- lib/epitools/core_ext/numbers.rb,
lib/epitools/core_ext/truthiness.rb
Constant Summary collapse
- BASE_DIGITS =
Cached constants for encoding numbers into bases up to 64
[*'0'..'9', *'A'..'Z', *'a'..'z', '_', '-']
- SMALL_POWERS_OF_2 =
{2=>1, 4=>2, 8=>3, 16=>4, 32=>5, 64=>6}
Instance Method Summary collapse
-
#blank? ⇒ Boolean
'true' if the integer is 0.
-
#fact ⇒ Object
(also: #factorial)
Factorial.
-
#factors ⇒ Object
Returns the all the prime factors of a number.
-
#fib ⇒ Object
(also: #fibonacci)
Fibonacci (recursive style).
- #integer? ⇒ Boolean
-
#invert ⇒ Object
Flip all bits except the sign bit.
-
#prime? ⇒ Boolean
Am I a prime number?.
-
#primes(starting_at = 2) ⇒ Object
Return a specified number of primes (optionally starting at the argument).
-
#to_base(base = 10) ⇒ Object
Convert a number into a string representation (encoded in a base <= 64).
- #to_base62 ⇒ Object
-
#to_bits ⇒ Object
(also: #bits)
Convert the number to an array of bits (least significant digit first, or little-endian).
-
#to_hex ⇒ Object
Convert the number into a hexadecimal string representation.
Instance Method Details
#blank? ⇒ Boolean
'true' if the integer is 0
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# File 'lib/epitools/core_ext/truthiness.rb', line 61 def blank?; self == 0; end |
#fact ⇒ Object Also known as: factorial
Factorial
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# File 'lib/epitools/core_ext/numbers.rb', line 350 def fact if self < 0 -(1..-self).reduce(:*) elsif self == 0 1 else (1..self).reduce(:*) end end |
#factors ⇒ Object
Returns the all the prime factors of a number.
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# File 'lib/epitools/core_ext/numbers.rb', line 342 def factors Prime # autoload the prime module prime_division.map { |n,count| [n]*count }.flatten end |
#fib ⇒ Object Also known as: fibonacci
Fibonacci (recursive style)
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# File 'lib/epitools/core_ext/numbers.rb', line 364 def fib self < 2 ? self : (self-1).fib + (self-2).fib end |
#integer? ⇒ Boolean
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# File 'lib/epitools/core_ext/truthiness.rb', line 63 def integer?; true; end |
#invert ⇒ Object
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.)
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# File 'lib/epitools/core_ext/numbers.rb', line 376 def invert to_s(2).tr("01","10").to_i(2) end |
#prime? ⇒ Boolean
Am I a prime number?
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# File 'lib/epitools/core_ext/numbers.rb', line 319 def prime? Prime.prime? self end |
#primes(starting_at = 2) ⇒ Object
Return a specified number of primes (optionally starting at the argument)
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# File 'lib/epitools/core_ext/numbers.rb', line 326 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 |
#to_base(base = 10) ⇒ Object
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)
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# File 'lib/epitools/core_ext/numbers.rb', line 282 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 |
#to_base62 ⇒ Object
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# File 'lib/epitools/core_ext/numbers.rb', line 312 def to_base62 to_base(62) end |
#to_bits ⇒ Object Also known as: bits
Convert the number to an array of bits (least significant digit first, or little-endian).
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# File 'lib/epitools/core_ext/numbers.rb', line 262 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 |
#to_hex ⇒ Object
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.)
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# File 'lib/epitools/core_ext/numbers.rb', line 255 def to_hex "%0.2x" % self end |