CompSci 4Chap 9 Sec 1 Oct 30, 2007Prof. Susan RodgerAnnouncements• Read Chapter 9, Sec 2 for next time• Assignment 6 due next Tuesday• Today– Chapter 9, Section 1 – Lists– Show Halloween card….Collections• In some animations, several objects must perform the same actions– Example: marching band marching• It is convenient to collect all objects into a group (collection)– Major benefit – write code for all the objects in the group (rather than separate code for each object)List• A list - one way to organize objects into a collection– You may use lists to organize• Shopping list• Todo list• In programming, a list is a collection of objects or information. We call an organizing structure a data structure.Creating Lists• In Alice, a list can be a list of numbers, or a list of objects, or a list of colors, etc.• Let’s create a list of skeletonsCreate List (cont)• Type in name• Select type• Select “make a list”• Add skeletons to list (click “new item” 4 times)•Result is:Programming with a List• Can “iterate through a list”– Do something to each item in the list• In order (use “For all in order”)• All together (use “For all together”)Example/Demo: Iteration in OrderFor each skeleton in orderskeleton says “Boo”For each skeleton in orderskeleton turns its head aroundApplying a Part of an object• Drag in skeleton turn• Select part• Drag over part• Drag in item• Type in partExample/Demo: Iteration TogetherFor all skeleton togetherskeleton says “Boo”For all skeleton in togetherskeleton turns its head and neck aroundList Questions• What are differences between For all in order and For all together?• When would you want to use each of them?• What can you put in a list?• When can you refer to a part of an object in a list?Classwork today• Create a list of players • Make them do several
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