てかこれ新しいイテレータなんか作らなくてもiterator_valueでSFINAEされたiterator enter( iterator ); iterator leave( iterator );を定義すれば良いだけか
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てかこれ新しいイテレータなんか作らなくてもiterator_valueでSFINAEされたiterator enter( iterator ); iterator leave( iterator );を定義すれば良いだけか