rust 泛型02

定义一个求数组种最大值的泛型函数fn<T>largest(list: &[T]),

largest1: 瑕疵在传入的参数于只适用于实现了Copy特征的类型.

largest2: 添加Clone约束，改进后没有了参数类型的限制，但Clone会有额外的性能开销，会在堆上重新分配内存。

largest3：修改后返回引用类型，避免了参数只能使用实现了Copy特征类型的问题，且不会额外分配内存。

fn largest1<T: PartialOrd + Copy>(list: &[T]) -> T {
    let mut largest = list[0];

    for &item in list.iter() {
        if item > largest {
            largest = item;
        }
    }

    largest
} 

fn largest2<T: PartialOrd + Copy + Clone>(list: &[T]) -> T {
    let mut largest = list[0];

    for &item in list.iter() {
        if item > largest {
            largest = item;
        }
    }

    largest
}

fn largest3<T: PartialOrd>(list: &[T]) -> &T {
    let mut largest = &list[0];

    for item in list.iter() {
        if item > largest {
            largest = item;
        }
    }

    largest
}

fn main() {
    let number_list = vec![34, 50, 25, 100, 65];

    let result = largest3(&number_list);
    println!("The largest number is {}", result);

    let char_list = vec!['y', 'm', 'a', 'q'];

    let result = largest3(&char_list);
    println!("The largest char is {}", result);
}

 output:

The largest number is 100
The largest char is y