While loops

or... how to keep going until you get where you need to go!

What if you didn't know how big an island was, but you knew that somewhere, straight ahead, there was a row of flowers to be picked.

In the same way that Visual Basic allows a program to loop, Jeroo has a while loop to repeat lines of code as long as a condition is met.

The high-level algorithm is: Keep hopping as long as it's clear ahead, then keep picking flowers as long as there are flowers ahead.

The actual code for a Jeroo named jed is:

while( jed.isClear(AHEAD))
{
     jed.hop();                 // Keep hopping as long as it is clear ahead
}

while (jed.isFlower(AHEAD))
{
     jed.hop();
     jed.pick();                // Keep picking flowers as long as there are flowers ahead
}
 

This could be changed into an original method that any Jeroo could use as follows:

method pickARow()         // Pick a row of flowers that is somewhere ahead
{
   while( isClear(AHEAD))
   {
      hop();            // Keep hopping as long as it is clear ahead
   }

   while( isFlower(AHEAD))
   {
      hop();
      pick();           // Keep picking flowers as long as there are flowers ahead 
   }
} 

Open GardenIsland and create the following 4 Jeroos and have them each pick a row of flowers as shown below using the pickARow method defined above. Predict what will happen BEFORE you run the program, then give it a try.

• Will the program run?
• Where will each Jeroo end up?
• How many flowers will be picked?
• What if a Jeroo started out already on top of a flower, would the program still work?