Robot Simulator

Instructions

Write a robot simulator.

A robot factory's test facility needs a program to verify robot movements.

The robots have three possible movements:

• turn right
• turn left
• advance

Robots are placed on a hypothetical infinite grid, facing a particular direction (north, east, south, or west) at a set of {x,y} coordinates, e.g., {3,8}, with coordinates increasing to the north and east.

The robot then receives a number of instructions, at which point the testing facility verifies the robot's new position, and in which direction it is pointing.

• The letter-string "RAALAL" means:
  • Turn right
  • Advance twice
  • Turn left
  • Advance once
  • Turn left yet again
• Say a robot starts at {7, 3} facing north. Then running this stream of instructions should leave it at {9, 4} facing west.

Words

Define a robot tuple with slots x, y, and direction. The direction slot holds one of the symbols north, east, south, or west (declared in this exercise's vocabulary).

• <robot> ( x y direction -- robot ) — construct a robot.
• move ( robot instructions -- robot ) — apply a string of R, L, and A instructions and return the updated robot.