If expressions

You use if expressions exactly like if statements in other languages:

fn main() {
let x = 10;
if x < 20 {
println!("small");
} else if x < 100 {
println!("biggish");
} else {
println!("huge");
}
}
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In addition, you can use if as an expression. The last expression of each block becomes the value of the if expression:

fn main() {
let x = 10;
let size = if x < 20 { "small" } else { "large" };
println!("number size: {}", size);
}
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Speaker Notes

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.

When if is used in an expression, the expression must have a ; to separate it from the next statement. Remove the ; before println! to see the compiler error.