ld the body of the
closure—these are optional if the closure body is a single expression. The end
of the closure, after the curly brackets, needs a semicolon to complete the
`let` statement. The value returned from the last line in the closure body
(`num`) will be the value returned from the closure when it’s called, because
that line doesn’t end in a semicolon; just as in function bodies.
-->
<p>引数の後に、クロージャの本体を保持する波括弧を配置します(これはクロージ