# Composite

  class for "parent-children relation".

## method:

  `initialize(parent)`

    `parent` is a parent for self.

  `parent`

    my parent.

  `add(c)`

    add a child for self.

  `delete(c)`

    delete one of my childen.

  `die`

    self and children die.

  `killchildren`

    children die.

  `close`

    die and set "closed" true.

  `closed?`

  `canclose?`

    can I close?

  `showtree(indent=0)`

    print tree. for debug.