averaged_collection.rs

pub struct AveragedCollection {
  values: Vec<i32>,
  average: f64,
}

impl AveragedCollection {
  pub fn new(values: Vec<i32>) -> Self {
    let mut new_coll = Self {
      values,
      average: 0.0
    };
    new_coll.update_average();
    new_coll
  }

  pub fn add(&mut self, value: i32) {
    self.values.push(value);
    self.update_average();
  }

  pub fn remove(&mut self) -> Option<i32> {
    let result = self.values.pop();
    match result {
      Some(value) => {
        self.update_average();
        Some(value)
      },
      None => None,
    }
  }

  pub fn average(&self) -> f64 {
    self.average
  }

  fn update_average(&mut self) {
    let sum: i32 = self.values.iter().sum();
    self.average = sum as f64 / self.values.len() as f64;
  }
}

#[test]
fn ex1_avarage_basic() {
  let coll = AveragedCollection::new(vec![1,3]);
  assert_eq!(coll.average(), 2.0);
}