在包含元组的结构的 VecDeque 上使用 iter().map

Question

I am new in Rust. I have the following problem:

pub struct Events {
    pub ts: u64,
    pub temperature_multiplier: (f64,f64), // (temperature,multiplier)
}

I have a VecDeque of this struct

elements_vec: VecDeque<Events>

I would like to be able to go through all the elements of VecDeque and compute the the sum of (temperature * multiplier).

What I have tried:

elements_vec.iter().map(|(_, (t,m))| t * m ).sum()

It returns an error saying "expected Struct Events".

Answer 1

Events is not a tuple but a struct. You need to go through Destructuring Structs section in rust book .

elements_vec.iter().map(|Events { temperature_multiplier: (t, m), .. }| t * m).sum::<f64>()

Answer 2

This is how I understood your question:

let mut elements_vec: VecDeque<Events> = VecDeque::with_capacity(10);
elements_vec.push_back(Events { ts: 0x0002, temperature_multiplier: (20.0, 2.0) });
elements_vec.push_back(Events { ts: 0x0003, temperature_multiplier: (30.0, 3.0) });
elements_vec.push_front(Events { ts: 0x0001, temperature_multiplier: (10.0, 1.0) });

println!("{:?}", &elements_vec);

let s : f64 = elements_vec.iter().map(|evnt| evnt.temperature_multiplier.0 * evnt.temperature_multiplier.1 ).sum();

println!("s: {}", s); // s: 140

The answer is in the compiler's message: map() needs struct Events , which we give it as map(|evnt| /* and use it here */) . And it works!