he
*definition* of an anonymous function, not the *resulting value* of calling the
anonymous function. Recall that we’re using a closure because we want to define
the code to call at one point, store that code, and call it at a later point;
the code we want to call is now stored in `expensive_closure`.
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<p>この<code>let</code>文は、<code>expensive_closure</code>が、匿名関数を呼び出した<em>結果の値</em>ではなく、
匿名関数の<em>定義</em>を含むことを意味するこ�