沿维度的求和数组 [英] Sum array along dimension

问题描述

在许多语言（Fortran，Matlab / Octave，Julia等）中，诸如 sum（array，n）之类的表达式将沿n求和一个数组的值：维度并输出一个较低维度的数组。 Rust中有等同的东西吗？

In many languages (Fortran, Matlab/Octave, Julia, etc) an expression like sum(array,n) will sum the values of an array along the n:th dimension and outputting an array of one lower dimensionality. Is there something equivalent in Rust?

我尝试过：

fn main() {
    let arr1: [f64; 5] = [1.1, 1.2, 2.3, 3.4, 4.5555];
    println!("this {}", arr1.iter().sum())
}

，出现以下错误：

error[E0282]: unable to infer enough type information about `_`
 --> src/main.rs:3:37
  |
3 |     println!("this {}", arr1.iter().sum())
  |                                     ^^^ cannot infer type for `_`
<std macros>:2:27: 2:58 note: in this expansion of format_args!
<std macros>:3:1: 3:54 note: in this expansion of print! (defined in <std macros>)
src/main.rs:3:5: 3:43 note: in this expansion of println! (defined in <std macros>)
  |
  = note: type annotations or generic parameter binding required

推荐答案

在这种情况下，您必须明确指定元素的类型：

In this case you have to explicitly specify type of the elements:

println!("this {}", arr1.iter().sum::<f64>())

您非常亲密:)

@ E_net4建议的另一种选择是使用单独的绑定：

Another option that were suggested by @E_net4 is to use separate binding:

let res: f64 = arr1.iter().sum();
println!("this {}", res)

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