��ている値を借用します。データを参照すること以外に特別な能力は何もありません。
また、オーバーヘッドもなく、ポインタの中では最も頻繁に使われます。</p>
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*Smart pointers*, on the other hand, are data structures that not only act like
a pointer but also have additional metadata and capabilities. The concept of
smart pointers isn’t unique to Rust: smart pointers originated in C++ and exist
in other languages as well. In Rust, the differ