Page 239 - Learn To Program With Scratch

Before After
Drop-down
menu

Figure 9-6: A list before and after add and delete are used
to change its contents

The add command is straightforward, but let’s examine the delete
command more closely. You can type the index of the element you want to
delete directly into the block’s parameter slot, or you can click the drop-
down arrow. The drop-down menu (see Figure 9-6) shows three options:
1, last, and all. Select 1 to delete the first item (“Apple”) from the list, select
last to delete the last item (“Mango”), or select all to delete all the items
from the list.

Insert and Replace
Let’s say you want to store your friends’ names and phone numbers alpha-
betically in a list, just like the contacts list in your cell phone. As you make
your list, you need to insert each friend’s contact information at the proper
position. Later, if one friend gets a new phone number, you’ll need to edit
the list to enter it. The insert and replace commands can help you with
these tasks. Figure 9-7 shows an example of using the insert and replace
commands with our phone list.
Before Drop-down We used the replace After
menu command to change
Kim’s phone number.
Mark is now at the
4th position. Paul is
pushed down to the
5th position.

Figure 9-7: Using the insert and the replace commands to update a list of telephone numbers

The replace command overwrites the current string at slot number
3 with Kim’s new phone number. The insert command places the phone
number of a new friend, Mark, at slot number 4 in the list. Notice that the
existing elements moved down one slot to make room for the new entry.
Clicking the item number’s down arrow in both the replace and the
insert commands shows a drop-down menu of three options: 1, last, and
random (see Figure 9-7). If you select random, the selected command will
choose an item number randomly. You’ll see some useful applications of
this feature later in this chapter.

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