Rot13

rot_13.rb

def rot13(ascii_char)
  ascii_offset  = 65
  alphabet_size = 26
  full_index    = ascii_char.ord - ascii_offset
  cap_bit       = full_index & 0b100000
  half_index    = full_index & 0b011111
  rotated       = (half_index + alphabet_size/2) % alphabet_size
  (rotated + cap_bit + ascii_offset).chr
end

"Va beqre gb trarengr gur vaivgr pbqr, znxr n CBFG erdhrfg gb /ncv/vaivgr/trarengr"
  .gsub /\w/, &method(:rot13)
  # => "In order to generate the invite code, make a POST request to /api/invite/generate"

"Va beqre gb trarengr gur vaivgr pbqr, znxr n CBFG erdhrfg gb /ncv/vaivgr/trarengr"
  .gsub(/\w/) { |c| (((c.ord-65 & 31)+13)%26 + 65 | c.ord&32).chr }
  # => "In order to generate the invite code, make a POST request to /api/invite/generate"

"Va beqre gb trarengr gur vaivgr pbqr, znxr n CBFG erdhrfg gb /ncv/vaivgr/trarengr".gsub(/\w/) { |c|
  n = c.ord
  n -= 65
  n &= 31
  n += 13
  n %= 26
  n += 65
  n |= c.ord&32
  n.chr
}
# => "In order to generate the invite code, make a POST request to /api/invite/generate"