1569-cache-invalidation-distance-limit.yaml

version: 1
name: Pathfinding cache - changing distance limit
description: |
  Demonstrates various sequences of distance limit increases and decreases.
creative: false
objectives:
  - goal:
      - Make lemonade
    condition: |
      as base {
        has "lemonade";
      };
solution: |
  def go =

    // The cache gets initially populated with an
    // unlimited distance, so in a sequence of
    // (1) a decreased limit followed by
    // (2) an increased finite limit,
    // the increase in (2) is still considered a decrease
    // relative to the cache.

    // Invocation #1: Expect RECOMPUTATION
    path (inL ()) (inR "flower");

    // Invocation #2: Expect SUCCESS
    path (inL ()) (inR "flower");

    // Invocation #3: Expect SUCCESS
    path (inR 5) (inR "flower");

    // Invocation #4: Expect SUCCESS
    // Even though this is an increase relative to the previous invocation,
    // it is a decrease relative to the cached limit.
    path (inR 6) (inR "flower");

    move;

    // Invocation #5: Expect RECOMPUTATION
    // We have invoked 'path' from a new location, so evict the cache.
    path (inR 6) (inR "flower");

    // Invocation #6: Expect SUCCESS
    path (inR 4) (inR "flower");

    // Invocation #7: Expect RECOMPUTATION
    path (inR 7) (inR "flower");

    // Invocation #8: Expect SUCCESS
    path (inR 5) (inR "flower");

    // Invocation #9: Expect FAILURE
    // This failure is not cached.
    path (inR 2) (inR "flower");

    // Invocation #10: Expect SUCCESS
    // The cache is still valid from the previous success.
    path (inR 4) (inR "flower");

    make "lemonade";
    end;

  go;
entities:
  - name: wayfinder
    display:
      char: 'w'
    description:
      - Enables `path` command
    properties: [known, pickable]
    capabilities: [path]
  - name: monolith
    display:
      char: '@'
      attr: rock
    description:
      - Pushable rock
    properties: [known, unwalkable, pickable]
  - name: lemon
    display:
      char: 'o'
      attr: gold
    description:
      - Sour fruit
    properties: [known, pickable]
  - name: lemonade
    display:
      char: 'c'
      attr: gold
    description:
      - Sweet drink
    properties: [known, pickable]
recipes:
  - in:
      - [1, lemon]
    out:
      - [1, lemonade]
robots:
  - name: base
    dir: north
    devices:
      - ADT calculator
      - antenna
      - branch predictor
      - comparator
      - compass
      - dictionary
      - linotype
      - logger
      - grabber
      - toolkit
      - treads
      - wayfinder
      - workbench
    inventory:
      - [1, lemon]
known: [flower]
world:
  palette:
    'B': [grass, erase, base]
    '.': [grass]
    'f': [grass, flower]
  upperleft: [0, 0]
  map: |
    ....
    B..f
    ....