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Lecture 38: Typedefs

CSC 107 – Programming For Science. Lecture 38: Typedefs. Today’s Goal. Discover best uses of structures in a program Using typedef to make meaningful names. Creating A struct. Declare struct outside of any function After #include s where normally find declarations

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Lecture 38: Typedefs

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  1. CSC 107 – Programming For Science Lecture 38:Typedefs

  2. Today’s Goal • Discover best uses of structures in a program • Using typedef to make meaningful names

  3. Creating A struct • Declare structoutside of any function • After #includes where normally find declarations • Within struct, must declare 1 or more fields • Name & data type required for each field • Fields can be listed in any order • Any type can be used for fields, even struct typesstruct student { double gpa; char name[40];// Arrays are okayint *year;// Pointers fine, also};

  4. Using structs • Type of the variable is specific struct • Fields are like variable just as array entries are • Requires having actual variable to access • Each field is set & used independent of others • Code can access field as variableName.fieldName • No link between fields, even if from same struct

  5. Assigning structs • Like all variables, can assign structs • Identical struct type neededfor source & target • Works like assigning fields in source to fields in target • Primitive values are copied like primitive variables • With assignment, arrays & pointers alias same value • Fields just like variables of the same type • Can be used just like any variable of that type • Need struct to get access to the field initially

  6. Pointers to struct • Like all other types, can have pointer to struct • Assign using &to get address of struct variable • Can also dynamically allocate array using new • 2 ways to access fields with struct pointers • Follow pointer to struct & use the . operator(*pointerToStruct).fieldName • Use pointer operator, ->, to access field directlypointerToStruct->fieldName

  7. typedefs For Simplicity • Make synonyms for types using a typedef:typedeforiginal type new_name; • Simplify & clarify code by making types meaningful • Synonym only for coder; computer ignores difference • Really creates shorthand; does NOT make new type typedeflongBIG_INTEGER;typedefunsigned long bob;typedefchar * CSTRING;typedefstruct energy ENERGY;

  8. Will It Compile? typedefint MIDDLE;typedef char* CSTRING;typedefstruct energy ENERGY;MIDDLE i = 5;CSTRING str = “Bob”;struct energy ball;ENERGY *nerf = &ball;int j = i;strcpy(str, “Yo, whatup dog”);nerf = new struct energy[100];i++;str = new CSTRING[23];nerf = new ENERGY[12];nerf[2] = ball;str = new char[42];

  9. Will It Compile? typedefint MIDDLE;typedef char* CSTRING;typedefstruct energy ENERGY;MIDDLE i = 5;CSTRING str = “Bob”;struct energy ball;ENERGY *nerf = &ball;int j = i;strcpy(str, “Yo, whatup dog”);nerf = new struct energy[100];i++;str = new CSTRING[23];nerf = new ENERGY[12];nerf[2] = ball;str = new char[42];

  10. Will It Compile? typedefint MIDDLE;typedef char* CSTRING;typedefstruct energy ENERGY;MIDDLE i = 5;CSTRING str = “Bob”;struct energy ball;ENERGY *nerf = &ball;int j = i;strcpy(str, “Yo, whatup dog”);nerf = new struct energy[100];i++;str = new CSTRING[23];nerf = new ENERGY[12];nerf[2] = ball;str = new char[42];

  11. Will It Compile? typedefint MIDDLE;typedef char* CSTRING;typedefstruct energy ENERGY;MIDDLE i = 5;CSTRING str = “Bob”;struct energy ball;ENERGY *nerf = &ball;int j = i;strcpy(str, “Yo, whatup dog”);nerf = new struct energy[100];i++;str = new CSTRING[23];nerf = new ENERGY[12];nerf[2] = ball;str = new char[42];

  12. Will It Compile? typedefint MIDDLE;typedef char* CSTRING;typedefstruct energy ENERGY;MIDDLE i = 5;CSTRING str = “Bob”;struct energy ball;ENERGY *nerf = &ball;int j = i;strcpy(str, “Yo, whatup dog”);nerf = new struct energy[100];i++;str = new CSTRING[23];nerf = new ENERGY[12];nerf[2] = ball;str = new char[42];

  13. Will It Compile? typedefint MIDDLE;typedef char* CSTRING;typedefstruct energy ENERGY;MIDDLE i = 5;CSTRING str = “Bob”;struct energy ball;ENERGY *nerf = &ball;int j = i;strcpy(str, “Yo, whatup dog”);nerf = new struct energy[100];i++;str = new CSTRING[23];nerf = new ENERGY[12];nerf[2] = ball;str = new char[42];

  14. Will It Compile? typedefint MIDDLE;typedef char* CSTRING;typedefstruct energy ENERGY;MIDDLE i = 5;CSTRING str = “Bob”;struct energy ball;ENERGY *nerf = &ball;int j = i;strcpy(str, “Yo, whatup dog”);nerf = new struct energy[100];i++;str = new CSTRING[23];nerf = new ENERGY[12];nerf[2] = ball;str = new char[42];

  15. Will It Compile? typedefint MIDDLE;typedef char* CSTRING;typedefstruct energy ENERGY;MIDDLE i = 5;CSTRING str = “Bob”;struct energy ball;ENERGY *nerf = &ball;int j = i;strcpy(str, “Yo, whatup dog”);nerf = new struct energy[100];i++;str = new CSTRING[23];nerf = new ENERGY[12];nerf[2] = ball;str = new char[42];

  16. Will It Compile? typedefint MIDDLE;typedef char* CSTRING;typedefstruct energy ENERGY;MIDDLE i = 5;CSTRING str = “Bob”;struct energy ball;ENERGY *nerf = &ball;int j = i;strcpy(str, “Yo, whatup dog”);nerf = new struct energy[100];i++;str = new CSTRING[23];nerf = new ENERGY[12];nerf[2] = ball;str = new char[42];

  17. Will It Compile? typedefint MIDDLE;typedef char* CSTRING;typedefstruct energy ENERGY;MIDDLE i = 5;CSTRING str = “Bob”;struct energy ball;ENERGY *nerf = &ball;int j = i;strcpy(str, “Yo, whatup dog”);nerf = new struct energy[100];i++;str = new CSTRING[23];nerf = new ENERGY[12];nerf[2] = ball;str = new char[42];

  18. Will It Compile? typedefint MIDDLE;typedef char* CSTRING;typedefstruct energy ENERGY;MIDDLE i = 5;CSTRING str = “Bob”;struct energy ball;ENERGY *nerf = &ball;int j = i;strcpy(str, “Yo, whatup dog”);nerf = new struct energy[100];i++;str = new CSTRING[23];nerf = new ENERGY[12];nerf[2] = ball;str = new char[42];

  19. Will It Compile? typedefint MIDDLE;typedef char* CSTRING;typedefstruct energy ENERGY;MIDDLE i = 5;CSTRING str = “Bob”;struct energy ball;ENERGY *nerf = &ball;int j = i;strcpy(str, “Yo, whatup dog”);nerf = new struct energy[100];i++;str = new CSTRING[23];nerf = new ENERGY[12];nerf[2] = ball;str = new char[42];

  20. Your Turn • Get into your groups and try this assignment

  21. For Next Lecture • Spend 1 last day on structson Monday • Write better solution to well-known problem • Understand why structs used in real-world problems • Before moving on in class, solidify students knowledge • Angel has Weekly Assignment #14 for Tuesday • Last programming assignment due in 1 week

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