$ ri Array
---------------------------------------------------------- Module: Array
     Arrays are ordered, integer-indexed collections of any object.
     Array indexing starts at 0, as in C or Java. A negative index is
     assumed to be relative to the end of the array---that is, an index
     of -1 indicates the last element of the array, -2 is the next to
     last element in the array, and so on.
------------------------------------------------------------------------
Includes:
---------
     Enumerable(all?, any?, collect, detect, each_with_index, entries,
     find, find_all, grep, include?, inject, map, max, member?, min,
     partition, reject, select, sort, sort_by, to_a, zip)
Class methods:
--------------
     [], new
Instance methods:
-----------------
     &, *, +, -, <<, <=>, ==, [], []=, assoc, at, clear, collect,
     collect!, compact, compact!, concat, delete, delete_at, delete_if,
     each, each_index, empty?, eql?, fetch, fill, first, flatten,
     flatten!, frozen?, hash, include?, index, indexes, indices, insert,
     inspect, join, last, length, map, map!, nitems, pack, pop, push,
     rassoc, reject, reject!, replace, reverse, reverse!, reverse_each,
     rindex, select, shift, slice, slice!, sort, sort!, to_a, to_ary,
     to_s, transpose, uniq, uniq!, unshift, values_at, zip, |