以下是来自Rust by Example的示例:
fn is_odd(n: u32) -> bool {
n % 2 == 1
}
fn main() {
println!("Find the sum of all the squared odd numbers under 1000");
let upper = 1000;
// Functional approach
let sum_of_squared_odd_numbers: u32 =
(0..).map(|n| n * n) // All natural numbers squared
.take_while(|&n| n < upper) // Below upper limit
.filter(|n| is_odd(*n)) // That are odd
.fold(0, |sum, i| sum + i); // Sum them
println!("functional style: {}", sum_of_squared_odd_numbers);
}
为什么
take_while
的闭包使用引用传递其参数,而其他所有闭包都是按值传递?