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++:

1. fn main() {
2. let input = 'x';

4. match input {
5. 'q'                   => println!("Quitting"),
6. 'a' | 's' | 'w' | 'd' => println!("Moving around"),
7. '0'..='9'             => println!("Number input"),
8. _                     => println!("Something else"),
9. }
10. }

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.