In this task we have to guide the frog safely across a river.  The river is far too fast moving for the frog and it will drown if it falls in.  We can however hop onto either a passing lilly pad or a tree trunk, then continue moving right once we’re aboard.  Similar to the previous task involving traffic, we will have to wait for either a lilly pad or a tree trunk to arrive before we can cross.

nextToRiver() Evaluates to true if the frog is directly next to a river
nextToPad() Evaluates to true if there is a lilly pad near to the frog
nextToLog() Evaluates to true if there is a log near to the frog

Similar to the previous task, we need to move to the edge of the river and then loop while nextToRiver() is true.  This time however, we can use the instruction frogRight() when either nextToPad() or nextToLog() is true.

To do this we use the symbol '||', which is two | symbols back to back.  Programmers call this an 'Or operator'.  An expression, followed by ||, followed by another expression evaluates to true if either of the expressions is true.

First Expression Operator Second Expression Result
Is the world round?

||

 Is the sky blue? true
Is the world round?

||

 Is the sky green? true
Is the world flat?

||

 Is the sky blue? true
Is the world flat?

||

 Is the sky green? false

The if statement in the while loop will look like this:

if( nextToPad() || nextToLog() )
   frogRight(3);

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