Match expressions

match compares a value against a list of patterns and runs the first arm that fits. It is an expression, so the whole match has a value. The compiler insists the match is exhaustive: every possible value must be covered, or the code does not compile.

fn label(n: i32) -> &'static str {
    match n {
        0 => "zero",
        1 | 2 | 3 => "few",
        4..=9 => "several",
        x if x < 0 => "negative",
        _ => "many",
    }
}

Things to notice:

• | combines patterns and a..=b matches an inclusive range.
• x if x < 0 is a guard: the arm applies only if the extra condition is true. Here x is also a binding, a name for the matched value.
• _ matches anything and is the usual last arm. Arms are checked top to bottom, so order matters.

Patterns can take apart tuples too, binding pieces as they go:

match (a, b) {
    (0, _) => "first is zero",
    (_, y) => if y > 0 { "positive" } else { "other" },
}

Your task

The tests use everything below, so all of it must be pub.

1. pub enum Coin { Penny, Nickel, Dime, Quarter } (keep the derive line from the starter) and pub fn cents(c: Coin) -> u32 returning 1, 5, 10 and 25.
2. pub fn classify(n: i32) -> &'static str: "zero" for 0, "negative" for anything below 0, "small" for 1 to 9, and "large" otherwise.
3. pub fn locate(p: (i32, i32)) -> String: (0, 0) gives "origin", (x, 0) gives "x axis at {x}", (0, y) gives "y axis at {y}", and any other point gives "({x}, {y})", for example "(3, -4)".