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06+-+Arrays+and+Pointers

# 06+-+Arrays+and+Pointers - On to Arrays Data Types weve...

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9/1/10 1 Arrays and Pointers EECS 280 Programming and Introductory Data Structures On to Arrays Data Types we’ve seen so far… “atoms”: types with singleton values. For example, something of type “int” holds one “integer”. Something of type “char” holds one character. “aggregate” types: types that hold “sets” of values where each value is of some type. When all values have the same type, we call it a “homogeneous” aggregate, otherwise it is “heterogeneous”. These are sometimes also called “container” types, because they contain other types. The two we've seen so far, in the context of project 2, are lists and trees: each holds a collection of integers. On to Arrays Revisiting Lists Lists have an important restriction (i.e. you cannot talk about an arbitrary element of a list). You can only talk about “the first element” and “the rest of the list”. We say such a structure is “linked”; you have to move from one link to the next. For example, suppose we have the following list: ( 1 2 3 4 ) To talk about element “4”, you have to call list_rest three times (to skip past 1, 2, and 3), and then call list_first. Lists have an important advantage too: Because they are defined recursively, there is no "maximum- sized" list. A list can grow as large as it needs to be (assuming the resources of the computer are infinite). On to Arrays Revisiting Lists Arrays The C++ array structure In contrast to a list, C++ has a structure called an array . An array is a fixed-sized, indexed, homogeneous aggregate type (a collection of items, all of the same type.) To declare and define an array of four integers (the same size as our list above), we would say the following: int array[4]; Arrays The C++ array structure For comparison purposes, let's also declare and define an integer, foo: int foo; int array[4]; The environment that we get when we do this is: foo: array:

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9/1/10 2 Arrays Question: The C++ array structure int foo; int array[4]; What are the contents of “array” after this declaration? foo: array: Arrays Initializing an array You can also initialize the contents of an array in one line – just like with an int. However, we need some sort of notation to specify a set of numbers: int foo = 7; int array[4] = { 1, 2, 3, 4 }; The corresponding environment would look like this: foo: array: 7 4 3 2 1 Arrays Initializing an array You can also initialize the contents of an array in one line – just like with an int. However, we need some sort of notation to specify a set of numbers: int foo = 7; int array[4] = { 1, 2, 3, 4 }; The corresponding environment would look like this: foo: array: 7 4 3 2 1 This is called a “static initializer”. Arrays Accessing elements in an array You can access the contents of an array using an “index”. The index of the first array element is zero, the next is one, and so on.
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06+-+Arrays+and+Pointers - On to Arrays Data Types weve...

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