filter_map and flat_map in Rust

Mapping and filtering in one pass, and flattening nested structure.

fn main() {
    let raw = ["3", "x", "7", "", "12"];

    let nums: Vec<i32> = raw
        .iter()
        .filter_map(|s| s.parse().ok())
        .collect();
    println!("{:?}", nums);

    let words = ["hot key", "cold start"];
    let parts: Vec<&str> = words
        .iter()
        .flat_map(|line| line.split(' '))
        .collect();
    println!("{:?}", parts);

    let nested = vec![vec![1, 2], vec![3], vec![]];
    println!("{:?}", nested.into_iter().flatten().collect::<Vec<i32>>());
}

How it works

filter_map keeps every Some the closure returns.
flat_map maps to iterators and concatenates them.
flatten does the same for an iterator of collections.

Keywords and builtins used here

Vec
fn
i32
let
main
str

The run, in numbers

Lines: 19
Characters to type: 419
Tokens: 178
Three-star pace: 95 tpm

At the three-star pace of 95 tokens a minute, this run takes about 112 seconds.

Type this snippet

Step 4 of 5 in Adapters, step 4 of 14 in Iterators & closures.

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