Исправление kelyar, 22.02.14 23:45 (текущая версия) :
1.9.3p194 :004 > ar = [[2,3],[5,1],[6,8]] => [[2, 3], [5, 1], [6, 8]] 1.9.3p194 :005 > ar.map{|i| i[0]} => [2, 5, 6]
Исходная версия kelyar, 22.02.14 23:44:
1.9.3p194 :004 > ar = [[2,3],[5,1],[6,8]] => [[2, 3], [5, 1], [6, 8]]
1.9.3p194 :005 > ar.map{|i| i[0]} => [2, 5, 6]