quest – Rust: Combinators

Applied Intermediate

13 Combinators

Most match statements on Option have a one-word replacement. Transform the inside of an Option with map, then fold a whole parse-with-default flow into a single chain.

Step 1 / 2

In first_upper, uppercase the first character if there is one -- map, no match.

Hints

s.chars().next() is the Option<char> you start from.
.map(|c| c.to_ascii_uppercase()) transforms the inside without unwrapping.

13_combinators.rs

// uppercase the first character, if there is one -- no match / if
fn first_upper(s: &str) -> Option<char> {
    todo!()
}

Reset to starterCompiled in a sandbox; hidden checks must pass.

Reveal solution

fn first_upper(s: &str) -> Option<char> {
    s.chars().next().map(|c| c.to_ascii_uppercase())
}