version: 1
name: Require devices
description: |
  Learn how to require additional devices that would otherwise not be installed.
objectives:
  - goal:
      - The `build` command automatically installs devices that it knows
        will be required.  For example, if you `build {move}`, some `treads`
        will automatically be installed on the new robot since it needs
        them to `move`.
      - However, sometimes you need a device but `build` can't tell that
        you need it. In this case, you can use the special `require`
        command to require a particular device.  For example, if you
        `build {require "3D printer"; move}`, a 3D printer will be
        installed on the new robot even though it does not execute any
        commands that use a 3D printer.
      - Your goal is to pick a flower on the other side of the river and
        bring it back to your base.  You win when the base has a
        `periwinkle` flower in its inventory.
      - "Hint: robots will drown in the water unless they have a `boat` device
        installed!"
    condition: |
      try {
        as base {has "periwinkle"}
      } { return false }
entities:
  - name: periwinkle
    display:
      attr: flower
      char: '*'
    description:
    - A flower.
    properties: [known, infinite, portable]
solution: |
  def m5 = move; move; move; move; move end;
  build {
    require "treads";  // #540

    require "boat"; turn right;
    m5; f <- grab; turn back; m5; give base f
  }
robots:
  - name: base
    heavy: true
    dir: [0,1]
    display:
      char: Ω
      attr: robot
    devices:
      - logger
      - 3D printer
      - dictionary
    inventory:
      - [10, solar panel]
      - [10, logger]
      - [10, treads]
      - [10, boat]
      - [10, grabber]
      - [10, scanner]
known: [water]
world:
  default: [blank]
  palette:
    'Ω': [grass, null, base]
    '.': [grass]
    '~': [ice, water]
    '*': [grass, periwinkle]
    '┌': [stone, upper left corner]
    '┐': [stone, upper right corner]
    '└': [stone, lower left corner]
    '┘': [stone, lower right corner]
    '─': [stone, horizontal wall]
    '│': [stone, vertical wall]
  upperleft: [-1, 3]
  map: |
    ┌──────┐
    │..~~..│
    │..~~..│
    │Ω.~~.*│
    │..~~..│
    │..~~..│
    └──────┘