Rust regular expressions

So the remainder of Day4 problem looked like so:

———-

1. byr (Birth Year) - four digits; at least 1920 and at most 2002.

1. iyr (Issue Year) - four digits; at least 2010 and at most 2020.

2. eyr (Expiration Year) - four digits; at least 2020 and at most 2030.

3. hgt (Height) - a number followed by either cm or in:

   • If cm, the number must be at least 150 and at most 193.

   • If in, the number must be at least 59 and at most 76.

4. hcl (Hair Color) - a # followed by exactly six characters 0-9 or a-f.

5. ecl (Eye Color) - exactly one of: amb blu brn gry grn hzl oth.

6. pid (Passport ID) - a nine-digit number, including leading zeroes.

7. cid (Country ID) - ignored, missing or not.

———-

While the numbers are easier to handle, if the parsing from string to number works, then it’s just a matter of checking the ranges.

The eye colour is easy too, just check if the value is present in a set.

For the hgt,hcl and pid - seems more appropriate to use a regular expression matcher.

https://docs.rs/regex/1.4.5/regex/

The regular expressions for hcl and pid are straightforward

let rehcl = Regex::new(r"^#[[:xdigit:]]{6}$").unwrap();
let repid = Regex::new(r"^[0-9]{9}$").unwrap();

While the hgt can be matched with single regular expression, could not get how to extract the numeric part for further validation

let re = Regex::new(r"(?P<cmh>^[0-9]{3}cm$)|(?P<inh>^[0-9]{2}in$)").unwrap();

So I’ll match them separately.

As an optimization, I set the regular expressions and the hash set under lazy static.

https://docs.rs/lazy_static/1.4.0/lazy_static/

Code here : https://github.com/aksharau/RustyAdventOfCode/tree/main/Day4/day4Part2

There is a lambda there, don’t kill me for instantiating it per call.

Also I came across this bizarre issue ( well, bizarre to me at-least ) : https://stackoverflow.com/questions/24502282/why-does-removing-return-give-me-an-error-expected-type-but-found-type

Neways, brag time folks!!