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Day 1: Historian Hysteria

Picat: Part 1 (00:14:24, rank 5509), Part 2 (00:21:04, rank 5393)

An incredibly simple problem for day 1. I managed to get stuck on the most basic input handling with Picat; hopefully I'm just a bit rusty with it. At some point I made at least the following errors:

  1. split(S) is NOT the same as split(s). The latter errors out with the message *** error(failed,main/0) and no stacktrace (possibly the worst thing about Picat, although that's probably just a Prolog thing since failures aren't always... failures...).

  2. zip in Picat produces an array, not a list. So this expression [abs(X-Y) : [X,Y] in zip(A,B)] always evaluates to the empty list due to pattern match failure. Instead you need to pattern match on an array: [abs(X-Y) : {X,Y} in zip(A,B)]. This is one of those areas where strong static typing would help. Makes me want to try Mercury again but the boilerplate for even a Hello World program is just too intimidating.

Timings (with hyperfine)

Part 1

Probably dominating by parsing.

Benchmark 1: picat part1.pi < input
  Time (mean ± σ):      20.8 ms ±   0.9 ms    [User: 9.8 ms, System: 11.0 ms]
  Range (min … max):    19.4 ms …  26.1 ms    138 runs

Part 2

Benchmark 1: picat part2.pi < input
  Time (mean ± σ):      20.2 ms ±   0.9 ms    [User: 10.1 ms, System: 10.7 ms]
  Range (min … max):    19.0 ms …  24.7 ms    132 runs