Pattern Matching

The match keyword let you match a value against one or more patterns. The comparisons are done from top to bottom and the first match wins.

The patterns can be simple values, similarly to switch in C and C++:

fn main() {
    let input = 'x';

    match input {
        'q'                   => println!("Quitting"),
        'a' | 's' | 'w' | 'd' => println!("Moving around"),
        '0'..='9'             => println!("Number input"),
        _                     => println!("Something else"),
    }
}

The _ pattern is a wildcard pattern which matches any value.

Key Points:

You might point out how some specific characters are being used when in a pattern
- | as an or
- .. can expand as much as it needs to be
- 1..=5 represents an inclusive range
- _ is a wild card
It can be useful to show how binding works, by for instance replacing a wildcard character with a variable, or removing the quotes around q.
You can demonstrate matching on a reference.
This might be a good time to bring up the concept of irrefutable patterns, as the term can show up in error messages.

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Pattern Matching

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