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.

The direction the robot is facing will be expressed as one of the following numbers:

• North = 0
• East = 1
• South = 2
• West = 3

When the input is invalid, return a direction of -1 (the other values will be ignored).

Reserved Memory

The buffer for the input string uses bytes 64-319 of linear memory.

The input string can be modified if desired.