Robbie the Robot is touring New Orleans and has discovered that an excellent oyster po-boy can be found at the Acme Oyster House in the French Quarter as shown below on 2nd Avenue at point Y. Currently he is standing a point X on A Street. Some of the street segments are one-way as indicated, but the two segments with ?-marks are both either 1-way east or 1-way west, depending upon traffic conditions and do not change during the course of a single trip from X to Y or from Y to X.
 

Robbie also has 9 friends with him at point X, and his job is to get a po-boy for each of his friends and return to point X to dine with them. He can only carry one meal at a time, which is of no consequence, since Robbie is, of course, only a robot. However, Robbie is to travel the shortest distance possible, considering the state of the one-way streets as he travels. On one trip he may be able to move east on 2nd Avenue, while on another he may have to take another route.

 Your job is to present Robbie's task as a formal algorithm.

Robotspeak

Robbie will move one block at a time when given one of the commands, NORTH;, EAST;, SOUTH;, or WEST;. For example, to get from point X to point Z simply requires the commands, NORTH;, and then WEST;. We can make more complicated commands by enclosing component commands in braces, as in {NORTH; WEST;}. Robbie can make decisions, too, using a function called LEGAL. For example, at some point he wants to know if it is legal to go west a block from where he is, so he can look at the value of LEGAL (WEST), which is YES if it is legal to go west and NO if it is not. In an algorithm one would write IF LEGAL (WEST) {Commands} to perform {Commands} only if it was legal to move west. One could also write IF LEGAL (WEST) {Commands 1} ELSE {Commands 2} if one wanted to perform different commands, depending on whether a move west was legal. Finally, there is a REPEAT command, in case one wanted to repeat a group of commands several times. For example, REPEAT (5) {commands} would repeat {commands} five times.

 A formal algorithm is written ALGORITHM (Name) {commands}, and in an algorithm we write lots of comments (lines beginning with an !) so that humans can figure out what is going on at any point in the algorighm. For example, if Robbie wants to take a walk around Acme from point X one could write,
  

   ALGORITHM (Circle Walk)

   ! This algorithm describes what Robbie does to take a walk around his favorite
   ! restaurant at point Y, starting with a southward move from point X.

   ! Move down to 1st Avenue.

     {SOUTH;
   
   ! Can't go up C Street since it's one-way in the wrong direction.

      REPEAT (3)
        {EAST;
        };

   ! Now continue north, then west, and then south back to the starting
   ! point.

     REPEAT (2)
       {NORTH;
       };
     REPEAT (3)
       {WEST;
       };
     REPEAT (2)
       {SOUTH;
       };
     }
Notice the consistent use of indentation, punctuation, blank lines, comments, and other documentation to make the formal algorithm into an unambiguous statement of what Robbie does to accomplish the assigned task.

 U-Turn Example