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");}}
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);}
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.