AoC day 3, part 1 (Smalltalk)

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

" Some conventient covering extensions: "
String extend [
    asRadix: rad [ ^Number readFrom: (ReadStream on: self) radix: rad ]
]

Collection extend [
    apply: method  [ ^self collect: [:x | x perform: method] ]
]

Array class extend [
    new: size withAllNew: class [ ^(1 to: size) collect: [:x| class new] ]
]


"
| Mainline
"
input := stdin lines contents.

" Collect bit-characters in an Array (index by position) of Bags "
counts := input inject: (Array new: 12 withAllNew: Bag) into: [:acc :line |
              acc with: line do: [ :bag :digit |
                  bag add: digit
              ]
          ].

" Get the most common ones for each position, read as a binary digit string "
gamma := (counts collect: [ :bag |
             bag sortedByCount first value
         ]) asString asRadix: 2.

" Epsilon is just gamma with bits XOR'd "
('Part 1: %1' % {gamma * (gamma bitXor: 16rFFF)}) displayNl.