aoc_1_with_types.roc

app "cli-tutorial"
    packages { pf: "../examples/cli/platform" }
    imports [ pf.Stdout, pf.Task.{ await } ]
    provides [ main ] to pf


Option a : [ Some a, None ]a
Aggr : { counts: Nat, previousElement: Option Nat}

initialState: Aggr
initialState = { counts: 0, previousElement: None }

walkStep: Aggr, Nat -> Aggr
walkStep = \state, elem ->
    when state.previousElement is
        Some previousElement if previousElement < elem -> { counts: state.counts + 1, previousElement: Some elem }
        _ -> { state & previousElement: Some elem }

measurements : List Nat
measurements = [199, 200, 208, 210, 200, 207, 240, 269, 260, 263 ]

increases: Aggr
increases = List.walk measurements initialState walkStep

increasesStr = Num.toStr increases.counts

main =
    {} <- await (Stdout.line "There are \(increasesStr) increases")
    Task.succeed {}