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Typedefs & Enums

Typedefs & Enums. Tricks for naming things. Typedef. typedef creates a new name for existing type Does not create new types! typedef exitingType newName ; Ex: typedef int number ; number x = 10; //number really means int. Why Typedef. Good uses Ugly constructs:

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Typedefs & Enums

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  1. Typedefs & Enums Tricks for naming things

  2. Typedef • typedefcreates a new name for existing type • Does not create new types! typedef exitingType newName; • Ex: typedefintnumber; number x = 10; //number really means int

  3. Why Typedef • Good uses • Ugly constructs: std::vector<std:pair<int, int> >::iterator myIt; std::vector<std:pair<int, int> >::iterator myOtherIt; Vs: typedef std::vector<std:pair<int, int> >::iterator VectorPairIterator; VectorPairIterator myIt; VectorPairIterator myOtherIt;

  4. Why Typedef • Good uses • Dealing with platform issues //On PC:typedefintint32;//On arduino processortypedeflong int32; //anywhere: int32 myNum; //int32 definitely has 32 bits

  5. Constant Issue • Constants = readable code

  6. Constant Issue • Don't protect us from stupidity:

  7. Enums • Enumerated Type • Custom data type with discrete set of possible values A weekday is something from:{Monday, Tuesday, Wednesday, Thursday, Friday}

  8. Enums • Syntax: enum newType {valueList}; • Sample enums: enum standing {FRESHMAN, SOPHOMORE, JUNIOR, SENIOR}; enum color {RED, BLUE, GREEN, BLACK, ORANGE};

  9. Enum Use • Enumusage • Can make variables of that type • Variables can only have given values enum standing{FRESHMAN, SOPHOMORE, JUNIOR, SENIOR}; standingstudentYear = FRESHMAN; standing student2Year = 12; //Error

  10. Enums • Pluses of constants, without dangers

  11. Enum Rules • Enum values must be valid identifiers • Start with letter, no special symbols, etc…

  12. Enum Rules • Enum values must be valid identifiers • Can't reuse identifiers

  13. Enum Values • Enums stored as integral values • Starting from 0: {Monday, Tuesday, Wednesday, Thursday, Friday} 0 1 2 3 4

  14. Enum Values • Enums stored as integral values • Can modify by assigning {Monday, Tuesday, Wednesday, Thursday, Friday} 10 11 30 31 32

  15. Enum Values • Only use assignment/value if represent logical value:

  16. Relational Operators • Relational operations work based on assigned values (order of enumerated values)

  17. Interacting: • Cin can't read into enum type • Read in string/int, use if:

  18. Interacting: • Cout will print as number • Print using if/switch/array

  19. Interacting: • Legal to switch based on enum:

  20. Integral Values • Math with enum results in an int

  21. Integral Values • Can static cast into an enum • Back to being dangerous

  22. Integral Values • Can static cast into an enum • Back to being dangerous • Better:

  23. Enum Passing • Work normally as parameteror return type:

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