我想编写一个函数,将零到n的数字相加。 (理想情况下,这对所有数字都是通用的,但我将满足i32
的要求)。
mod squares {
pub fn sum_from_zero( n: i32) -> i32 {
[0 .. n].fold(0, |a, b| a + b)
}
}
#[test]
fn test_sum_from_zero() {
assert_eq!(15, squares::sum_from_zero(5));
}
我收到以下编译器错误:
src/lib.rs:5:18: 5:22 error: no method named `fold` found for type `[std::ops::Range<i32>; 1]` in the current scope
src/lib.rs:5 [0 .. n].fold(0, |a, b| a + b)
^~~~
src/lib.rs:5:18: 5:22 note: the method `fold` exists but the following trait bounds were not satisfied: `[std::ops::Range<i32>; 1] : std::iter::Iterator`, `[std::ops::Range<i32>] : std::iter::Iterator`
我也尝试过使用
sum()
:mod squares {
pub fn sum_from_zero( n: i32) -> i32 {
[0 .. n].sum()
}
}
#[test]
fn test_sum_from_zero() {
assert_eq!(15, squares::sum_from_zero(5));
}
并得到以下编译器错误:
src/lib.rs:5:18: 5:21 error: no method named `sum` found for type `[std::ops::Range<i32>; 1]` in the current scope
src/lib.rs:5 [0 .. n].sum()
^~~
src/lib.rs:5:18: 5:21 note: the method `sum` exists but the following trait bounds were not satisfied: `[std::ops::Range<i32>; 1] : std::iter::Iterator`, `[std::ops::Range<i32>] : std::iter::Iterator`
src/lib.rs:5:18: 5:21 error: no method named `sum` found for type `[std::ops::Range<i32>; 1]` in the current scope
src/lib.rs:5 [0 .. n].sum()
^~~
src/lib.rs:5:18: 5:21 note: the method `sum` exists but the following trait bounds were not satisfied: `[std::ops::Range<i32>; 1] : std::iter::Iterator`, `[std::ops::Range<i32>] : std::iter::Iterator`
我必须声明明确的界限/特征吗?
最佳答案
问题是您要创建一个范围数组(方括号),但您只想要该范围(定义折叠的范围)。
另一件事是范围语法(..
)仅包含下限。它不包括上限,因此您必须迭代到n+1
才能获得所需的结果。
mod squares {
pub fn sum_from_zero( n: i32) -> i32 {
(0 .. n+1).fold(0, |a, b| a + b)
}
}
#[test]
fn test_sum_from_zero() {
assert_eq!(15, squares::sum_from_zero(5));
}
关于rust - 如何在Rust中求和一定范围的数字?,我们在Stack Overflow上找到一个类似的问题:https://stackoverflow.com/questions/40194949/