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C structs

C structs. Complex datatypes. So far, we’ve only discussed primitive C data types. A struct is a complex datatype that can consist of Primitive datatypes Ints, floats, chars Arrays of any of the above Pointers to primitive datatypes Other structs or pointers to other structs.

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C structs

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  1. C structs Complex datatypes CE-2810 Dr. Mark L. Hornick

  2. So far, we’ve only discussed primitive C data types A struct is a complex datatype that can consist of • Primitive datatypes • Ints, floats, chars • Arrays of any of the above • Pointers to primitive datatypes • Other structs • or pointers to other structs CS-280 Dr. Mark L. Hornick

  3. Suppose we want to declare a complex datatype to represent a Point (cartesian) struct Point { // declaration of Point float x; // x coordinate float y; // y coordinate }; To define a variable that is a Point, we write: struct Point point1; // unitialized struct Point point2; // unitialized The declaration is typically placed outside function bodies. CE-2810 Dr. Mark L. Hornick

  4. A struct can be initialized in a couple of ways To define and initialize a variable that is a Point, we write either: struct Point point1 = {1.0,2.0}; struct Point point2; // uninitialized point2.x = 3.0; point2.y = 4.0; The period is known as the structure member operator, Similar to the dot operator used in Java. CE-2810 Dr. Mark L. Hornick

  5. Suppose we want to declare a Rectangle that contains two Points struct Rect{ // declaration of Rect struct Point p1; // upper left struct Point p2; // lower right }; To define a variable that is a Rect, we write: struct Rect r1; struct Rect r2; CE-2810 Dr. Mark L. Hornick

  6. A Rect can be initialized in a couple of ways To define and initialize a variable that is a Rect, we write: struct Rect r1 = { {1,2}, {3,4} }; Struct Rect r2; // unitialized r2.p1.x=1.0; r2.p1.y=2.0; r2.p2.x=3.0; r2.p2.y=4.0; CE-2810 Dr. Mark L. Hornick

  7. Declaration of a pointer to a struct First, say we have a Rect: struct Rect r1 = {{1,2},{3,4}}; To define and initialize a variable that is a pointer to Rect, we write: struct Rect* pRect = &r1; CE-2810 Dr. Mark L. Hornick

  8. Accessing struct elements via a struct pointer struct Rect r1; // uninitialized struct Rect* pRect = &r1; pRect->p1.x=1.0; pRect->p1.y=2.0; pRect->p2.x=3.0; pRect->p2.y=4.0; The “->” bigraph is the structure member operator you usewhen you have a pointer to a struct. CE-2810 Dr. Mark L. Hornick

  9. typedefs – aliases for datatypes • The C typedef statement allows you to do things like this: typedef float realnum ; // realnum is now a defined type realnum x; // define a variable of type realnum typedef float* PFLOAT; // PFLOAT is now a defined type PFLOAT px; // define a variable of type PFLOAT px = &x; CS-280 Dr. Mark L. Hornick

  10. typedefs – aliases for datatypes • The C typedef statement allows you to do things like this: typedef struct Point { // declaration of Point struct float x; // x coordinate float y; // y coordinate } Point; // definition of Point datatype typedef *Point POINTREF; // definition of POINTREF type Point pt1; // “object” of type Point POINTREF pPt1 = & pt1; // pointer to a Point object CS-280 Dr. Mark L. Hornick

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