AoC 2023 day 18, part 1 (Smalltalk)

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

"
| Mainline
"
area   := 0.
pos    := (0 @ 0).
trench := 0.

stdin linesDo: [ :line |
    parts := line subStrings.

    delta := parts second asNumber.
    vert := (parts first = 'U') | (parts first = 'D').
    (parts first = 'U') | (parts first = 'L') ifTrue: [ delta := delta * -1 ].

    vert ifTrue:  [ pos y: (pos y + delta) ]
         ifFalse: [ pos x: (pos x + delta) ].

    area := area + (delta * (vert ifTrue: [pos x] ifFalse: [-1 * pos y])).
    trench := trench + delta abs.
].

part1 := (area abs + trench) / 2 + 1.
('Part 1: %1' % {part1}) displayNl.