--- step(limit) {|n| ... }              ruby 1.7 feature
--- step(limit, step) {|n| ... }        ruby 1.7 feature

    self Ϥ step ­ʤ limit ۤ
    ޤǥ֥å򷫤֤ޤstep οǤޤ(
    ά 1)ޤlimit  step ˤ Float ʤɤ
    Ǥޤ

    step  0 ꤷ㳰 ArgumentError ȯޤ

    self ֤ޤ

    ruby 1.7 feature: Fixnum, Integer ưޤ
    ˤ Float  step Ǥ褦ˤʤޤ

        1.1.step(1.5, 0.1) {|n| p n}
        => 1.1
           1.2
           1.3
           1.4
           1.5

