Summary - Iterators
- Rust course
- Intermediate
- Lesson 53/115
- 5 min
Combine map, filter and collect to build a word filter.
Iterators summary
Every iterator implements the Iterator trait: type Item and fn next. Adapters (map, filter, take, zip, enumerate, chain) are lazy and return new iterators; consumers (collect, sum, count, fold, for) produce the result. collect can produce a Vec, String, HashSet or Result depending on the target type.
zip and fold
zip combines two iterators into pairs; fold reduces all elements to a single result starting from an initial value:
let adlar = ["Ali", "Ece"];
let puan = [70, 95];
for (a, p) in adlar.iter().zip(puan.iter()) {
println!("{a}: {p}");
}
let toplam = puan.iter().fold(0, |acc, p| acc + p); // 165sum, max and count are really special cases of fold.
Practice Score table
Combine the arrays ["Ali", "Ece"] and [70, 95] with zip and print each line as ad: puan. Then compute the sum with fold and print toplam N.
Starter code
fn main() {
// buraya yaz
}Sample solution
fn main() {
let adlar = ["Ali", "Ece"];
let puan = [70, 95];
for (a, p) in adlar.iter().zip(puan.iter()) {
println!("{}: {}", a, p);
}
let toplam = puan.iter().fold(0, |acc, p| acc + p);
println!("toplam {}", toplam);
}Expected output
Ali: 70 Ece: 95 toplam 165
Questions and answers
Review the lesson questions together with their answers. To test yourself, solve the lesson interactively.
1 What is <code>[1, 2, 3].iter().zip(["a", "b"].iter()).count()</code>?
- 5
- Panic
- 2 Correct answer
- 3
Explanation: zip stops when the shorter iterator runs out.
2 Reduce
let toplam = puan.iter().____(0, |acc, p| acc + p);let toplam = puan.iter().fold(0, |acc, p| acc + p);Explanation: fold takes an initial value and a combining closure.
3 Group summary
| Term | Meaning |
|---|---|
next() |
One step |
map/filter |
Lazy adapter |
collect |
Collects into a collection |
fold |
Reduces to one value |