Arrays, Pointers and Structures

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Arrays, Pointers and Structures

• CS-240
• Dick Steflik

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Pointers

• allow us to access something indirectly
• index of a book points to some topic in the body
  of a book
• street addresses in a telephone book point to
  where some lives in the community
• a forwarding address points to an address of
  where some one can be reached (pointer to a
  pointer)

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Arrays and Structures

• Arrays - ordered collections of objects, all of
  the same type
• int abc4
• Structure - a collection of objects of dissimilar
  types
• struct MyType int abc double def

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First Class Objects

• First Class Object
• can be manipulated in all of the usual ways
• are usually safer than Second Class Objects
• preserve value semantics
• obj2 obj1 (assignment)
• objtype a objtype b(a) (copy constructor)
• a b (overloaded assignment operators)
• usually implemented as a class
• can have bounds checking

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Second Class Objects

• Primitive types (arrays and structs)
• dont preserve value semantics
• are not as safe as First Class Objects
• no bounds checking on array indicies

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Standard template Library

• a standard set of templates and class templates
  that provide a set of First Class types
• was an extra in older compilers
• built into current generation of compilers

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vector

• vector is a template class that provides a First
  Class version of the array primitive
• vectorltintgt a(3)
• allocates a vector containing 3 integers
• vector methods
• size() - return of elements in the vector
• resize(n) - change the size of the vector to n
  elements

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include ltstdlib.hgt include ltiostream.hgt include
ltvector.hgt using namespace std int main()
const int DIFFERENT_NUMBERS 100 int
totalNumbers cout ltlt How many numbers?
cin gtgt totalNumbers vectorltintgt
numbers(DIFFERENT_NUMBERS 1) for (int I0
I lt numbers.size() 1) numbersI 0
for (int j0 j lt totalNumbers j)
numbersrand DIFFERENT_NUMBERS 1
for (int k1 k lt DIFFERENT_NUMBERS k)
cout ltlt k ltlt occurs ltlt numbersk ltlt
times ltlt \n return 0
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