AoC day 2, Smalltalk

#!/usr/local/bin/gst -q

parse_re := '(\d+)-(\d+) (.): (.*)$' asRegex.

part1 := 0.
part2 := 0.

stdin linesDo:
[
    :line |

    (line =~ parse_re) ifMatched: [ :results |
        " Aliases: "
        low  := results at: 1.
        high := results at: 2.
        let  := results at: 3.
        pass := results at: 4.

        " Part 1: "
        " Check for low-high occurrences of the letter in the password. "
        " Makes a regex that looks something like: ^([^a]*a[^a]*){1,3}$ "
        check_re := ('^([^', let, ']*', let, '[^', let, ']*){', low, ',', high, '}$') asRegex.

        (pass =~ check_re) ifMatched: [ part1 := part1 + 1 ].

        " Part 2: "
        " Check if low xor high position equals letter. "
        (((pass at: low asInteger) asString = let)
            xor: ((pass at: high asInteger) asString = let)) ifTrue:
        [
            part2 := part2 + 1.
        ]
    ]
].

stdout nextPutAll: ('Part 1: ', part1 asString); nl.
stdout nextPutAll: ('Part 2: ', part2 asString); nl.