PDE - Setting Up and Accessing Arrays Part 2 (Lesson)

Setting Up and Accessing Arrays Part 2

So What About the For Each Loops?

An array is always required to use the for each loop statements.  An array can already be create as in the cat examples or the array is created as the for each statement is created.  The best use of these structures is for objects,  for example a group of animals on which the body of the for each statement, (the code in the block)  will operate. 

If numbers are used the numbers are "object" numbers.  To you nothing changes outwardly.  In the computer storage the item is an object when used within this type of loop.  

The for each structures apply and are used for objects.  

for each in: 

• • • reads an already created array data structure one at a time and executes the code block that you created. 
    • object array only and may be created with the for each in Together code statement block header.
    • provide a name for the generic item and in the set up heading and the array name. 
    • the looping stopped at the end of the array is handled for you.
    • not used for updating.

for each in Together: 

• • • reads an  array data structure completely, and all together executes the code block for all of the items at the same time.
    • object array only and may be created with the for each in Together code statement block header.
    • provide a name for the generic item and in the set up heading and the array name. 
    • the looping stopped at the end of the array is handled for you.
    • not used for updating.

The code and videos below will show the difference in operation of this array control structures.

Notes for the for each in and for each in code and video sets below.  

1. a is used to show that the variable is changed by the for each loop by each item read.  
2. a is initialized to -1, a number that is clearly not in the set of numbers to be used from the random pull from the numbers 0 - 99 (same code to load as on the prior page)
3. comment out of the update code is shown here to remind you that the for each is not used to update the array.  
4. the name given to the code item in the for each statement initializeIt or the initNbrSense becomes the name of each item in the body of the for each code.  This allows the data to be used in the same way for each of the items without having to use indexing for the position location.
5. view the videos and note the difference between the display of for each in and for each in together

For Each Code

For Each Video

Tips for Constructing Array Accessors

Below are tips for  constructing these array accessors.

Setup and Access of the for each Control Structures

Below is a video of the setup and access of the for each control structures, count, while, for each in, and for each in together as a summary of the ideas investigated in the last two pages.   Note that this allows programmers to control arrays that are only valid for the structure that they are created and used in. 

VIDEOS CREATED BY GAVS OR SOURCED FROM ALICE.ORG Links to an external site. AND USED ACCORDING TO TERMS OF USE.