Structs

1. Structs CSE 2451 Matt Boggus

2. Structures • Structure • one or more values, called members, with possibly dissimilar types that are stored together • Group together different types of variables under the same name • Compared to arrays • Data members may have different size • Not as easy to access members ( i.e. no [], use dot operator . instead ) • Structure variable names are not constant pointers like array names

3. Struct definition • struct <tag> {<member_list>} <variable_list>;

4. Example struct fraction { intnumerator; intdenominator; }; struct fraction f1, f2 = {.numerator = 1, .denominator = 1}; f1.numerator = 2; f1.denominator = 3; f2 = f1; if(f1 == f2) // invalid, == not defined for structs

5. Struct names/tags • The tag field sets a name to the struct • Allows creation of structures of the same type structPIXEL { float red; float green; float blue; } ; struct PIXEL p; struct PIXEL image[20], *imp;

6. Example of struct data members struct DATAMEMBERS { float f; // single variable inta[20]; // array long *lp; // pointer struct PIXEL pix; // a different struct struct PIXEL image[10]; // array of different structs struct PIXEL *imp; // pointer to a different struct } single, array [10];

7. Struct data member access • Dot operator ( . ) – for variables • struct_variable_name.member_name • Ex: single.f array[2].image[10].red • Indirection ( -> ) – for pointers • Pointer_to_struct->member_name • Ex: structDATAMEMBERS * s = &single; s->f Note: (*s).f == s->f

8. typedefs and structs • typedef<type> <name>; typedefstruct { float red; float green; float blue; } Pixel; Pixel p; Pixel image[100], *imp; • (Avoids the need to type struct in front of struct name)

9. Struct members of the same type struct SELF_REF1 { int a; struct SELF_REF1 b; }; Struct SELF_REF2 { int a; struct SELF_REF2 *b; };