--- find([ifnone]) {|item| ... }
--- detect([ifnone]) {|item| ... }

    ǤФƥ֥åɾͤˤʤäǽǤ֤ޤ
    ˤʤǤҤȤĤ⸫ĤʤäȤ ifnone (⤷
    ꤵƤ)ɾ nil ֤ޤ

    ifnone ˤʸ󤫤뤤ϡcall ᥽åɤĥ֥
    (㤨 Proc)ꤷޤ

        [1,2,3].find("raise") {|v| v > 4}
        # => -:1: unhandled exception

    ruby 1.7 feature: ifnone ʸϻǤʤʤޤ

