--- tsort_each {|node| ...}
#    is the iterator version of the tsort method.
#    obj.tsort_each is similar to obj.tsort.each but
#    modification of obj during the iteration may cause unexpected result.

    tsort ᥽åɤΥƥ졼ǤǤ
    obj.tsort_each  obj.tsort.each ȻƤޤ
    ֥åɾ obj ѹ줿ͽʤ̤ˤʤ
    Ȥޤ

#    tsort_each returns nil.
#    If there is a cycle, TSort::Cyclic is raised.

    tsort_each  nil ֤ޤ
    ϩ¸ߤȤ㳰 TSort::Cyclic 򵯤ޤ

