gistfile1.txt

ri 'Array#<=>'
= Array#<=>

(from ruby site)
------------------------------------------------------------------------------
  ary <=> other_ary   ->  -1, 0, +1 or nil

------------------------------------------------------------------------------

Comparison---Returns an integer (-1, 0, or +1) if this array is less than,
equal to, or greater than other_ary.  Each object in each
array is compared (using <=>). If any value isn't equal, then that inequality
is the return value. If all the values found are equal, then the return is
based on a comparison of the array lengths.  Thus, two arrays are ``equal''
according to Array#<=> if and only if they have the same length and the value
of each element is equal to the value of the corresponding element in the
other array.

  [ "a", "a", "c" ]    <=> [ "a", "b", "c" ]   #=> -1
  [ 1, 2, 3, 4, 5, 6 ] <=> [ 1, 2 ]            #=> +1