What you'll learn: Rust's control flow constructs —
if/elseas expressions,loop/while/for,match, and how they differ from C/C++ counterparts. The key insight: most Rust control flow returns values.
if is actually an expression, i.e., it can be used to assign values, but it also behaves like a statement. ▶ Try itfn main() {
let x = 42;
if x < 42 {
println!("Smaller than the secret of life");
} else if x == 42 {
println!("Is equal to the secret of life");
} else {
println!("Larger than the secret of life");
}
let is_secret_of_life = if x == 42 {true} else {false};
println!("{}", is_secret_of_life);
}
while keyword can be used to loop while an expression is truefn main() {
let mut x = 40;
while x != 42 {
x += 1;
}
}
for keyword can be used to iterate over rangesfn main() {
// Will not print 43; use 40..=43 to include last element
for x in 40..43 {
println!("{}", x);
}
}
loop keyword creates an infinite loop until a break is encounteredfn main() {
let mut x = 40;
// Change the below to 'here: loop to specify optional label for the loop
loop {
if x == 42 {
break; // Use break x; to return the value of x
}
x += 1;
}
}
break statement can include an optional expression that can be used to assign the value of a loop expressioncontinue keyword can be used to return to the top of the loopbreak or continue and are useful when dealing with nested loops{}. The evaluated value is simply the last expression in the blockfn main() {
let x = {
let y = 40;
y + 2 // Note: ; must be omitted
};
// Notice the Python style printing
println!("{x}");
}
return keyword in functionsfn is_secret_of_life(x: u32) -> bool {
// Same as if x == 42 {true} else {false}
x == 42 // Note: ; must be omitted
}
fn main() {
println!("{}", is_secret_of_life(42));
}