if 式
Rust の if 式 は、他の言語における if 文と全く同じように使えます。
さらに、if を式としても用いることができます。それぞれのブロックにある最後の式が、if 式の値となります。
Speaker Notes
This slide should take about 4 minutes.
Because if is an expression and must have a particular type, both of its branch blocks must have the same type. Show what happens if you add ; after "small" in the second example.
An if expression should be used in the same way as the other expressions. For example, when it is used in a let statement, the statement must be terminated with a ; as well. Remove the ; before println! to see the compiler error.