AoC day 16 (pt1), Smalltalk

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

" Split input by sections "
section := stdin contents tokenize: '\n\n'.

" First section: rules "
rules := (section first) tokenize: '\n'.

" Make set of all valid numbers to test against "
valid := Set new.
rules do: [ :s | (s =~ '(\d+)-(\d+) or (\d+)-(\d+)') ifMatched: [ :r |
                  (r at: 1) asNumber to: (r at: 2) asNumber do: [:n | valid add: n].
                  (r at: 3) asNumber to: (r at: 4) asNumber do: [:n | valid add: n].
              ].
          ].

" Third section: other tickets "
" Turn tickets into OrderedCollections of numbers "
others := ((section third) subStrings: Character nl) removeFirst; yourself.
others := (others collect: [:t | (t subStrings: '\n,') collect: [:n | n asNumber]]).

" Get invalid numbers from each ticket and sum them "
invalid := others collect: [:o | ((o reject: [:n | valid includes: n])
                                     inject: 0 into: [:a :b | a + b])].

" Sum over all tickets to get results "
stdout nextPutAll: ('Part 1: ', (invalid inject: 0 into: [:a :b| a + b]) asString); nl.