solve-2.ys

#!/usr/bin/env ys-0

defn safe?(report):
  or:
    actually-safe?: report
    safe-after-problem-dampener?: report

defn indices(coll):
  map-indexed _ coll:
    fn(i x): i

defn remove-by-index(i coll):
  keep-indexed _ coll:
    fn(j n):
       when (j != i): n

defn words-to-nums(s):
  s.words().map(to-num)

defn actually-safe?:
  (report):
    not:
      zero?:
        sum:
          map (fn [f] (actually-safe? report f)):
            list: (fn [a b] (- a b)) (fn [a b] (- b a))
  (report tester):
    first:
      reduce _ [1 report.first()] report.rest():
        fn([d a] b):
          list: (d * (if (<= 1 (tester a b) 3) 1 0)) b

defn safe-after-problem-dampener?(report):
  some truey?:
    map _ indices(report):
      fn(i):
        dampened-report =: remove-by-index(i report)
        actually-safe?: dampened-report

defn main():
  slurp("input"):lines.map(words-to-nums).filter(safe?):count:println