- each - Do block for each item. Works on hash or array. Can use 'break'. Return nothing.
- each_index - Same as each but pass in the index to the block
- collect (aka map) - Do block for each item. Return array. Same as Perl map.
- collect! / map! - Same as map, but modify array in place
- select (aka find_all) - Do block for each item. Return array if block is true. Same as Perl grep.
- select! (aka keep_if) - Same as select but modify array in place
- reject - Opposite of select. Return if block is false.
- reject! (aka delete_if) - Same as reject but modify array in place
- inject(xyzzy) (aka reduce) - Do block for each pair of items, starting with xyzzy & first item.
- compact - Return array with nil items removed
- compact! - Same as collect but modify array in place
- delete(foo) - Remove all items that are equal to foo
- clear - Remove all items
- empty? - Return true if array has no items
- count - Return number of items
- length (aka size) - Return number of items
- flatten! - Modify array to be 1-dimensional
- shuffle! - Shuffle in place
- sort! - Sort in place
- bsearch - Find item using binary search
- combination(3) - Return all combainations of length 3
- permutation(4) - Return all permutations of length 4
- sort_by! - Sort in place using keys in block
- transpose - swap rows and columns
- zip - step through two arrays at the same time
(source, source, source)