Repeating Actions

1. Repeating Actions

2. What will we learn today? • Repeated Actions • Need for Repetition • Repetition with Loop • Nested Loops

3. Repeated Actions in Real Life • Consider those daily actions • When we talk, we simply open and close our months repeatedly a counted number of times • When we walk, we move our legs forward and backward as we move a counted number of steps

4. Need for Repetition • Consider a situation in which a man walks 5 steps forward towards a palm tree • The man’s legs walk a step with each meter that he moves forward (if man moves forward 5 meters, his legs walking occur 5 times) • One possible way is to animate 5 steps • But, what if we want to repeat the walking action 20 times (becomes tedious and boring, isn’t it??)

5. Repetition with Loops • An easy way to do this is by using a loop statement • The Loop Statement • Is a simple way to repeat an action a counted number of times • Is used to execute a block of instructions again and again (limited number of times) • Is quick and easy to write and also easy to understand • A count is used to describe the number of times a loop/action(s) repeats

6. Hide and Seek Example with Loops • Remember the “hide and seek” example we did in the methods lecture • Remember how many times we had to animate(copy and past) the actions • Painful and tedious wasn’t it!!! • Now, the torture is over and we will use loops to make our lives simpler

7. Repetition with Loop • We have repeated actions in ‘Turn Around’ methods and in the ‘world.myfirst’ method • To create a loop in a program • Drag a loop tile into the editor inside the do-in order block of ‘world.myfirst’ method • Choose other and enter number 3 in the popup menu • Drag the ‘world.seekCat’ method into the loop statement • Inside the do-together block make two loops for the turning around methods

8. Nested Loops • A loop can be nested inside another loop (a loop is placed inside other loop) • Remember, the ‘move around’ method was used to make a complete turn around the tree (which requires repeating the moving a step and turning right actions ten times) • To make 3 complete turns we need to repeat the previous action 3 times Loop 3 times Loop 10 times Move Around

9. Nested Loop • The second loop ‘Loop 10 times’ is called a nested loop • It will fully execute each time the outer loop ‘loop 3 times’ executes once • The count of the outer loop is 3, and the count of the inner loop is 10 • The inner loop will execute 10 times for each of the 3 executions of the outer loop • The moving around action will occur 30 (3*10) times in total Loop 10 times Move Around

10. The Result Loop Statement

11. Turn Around methods with Loops

12. Let’s Work with Alice • Write an animation where an Arabian man in his tent serves coffee to his guests • Create a method ‘fill-inCups’ in which the host man holding the dallah (middle east) and fill-in 3 empty cubs in the tray (loop 3 times) • Create a method ‘serveCoffee’ where the host man serves his guests (loop 2 times) • Develop the animation for this story