Introduction to Structures

Objectives

1. Introduce structures.

Notes

• A tutorial
• For our word counting program we have a problem.
  • We need to store both a string and a count.
  • How can we do this
    • Parallel arrays are bad, they tend to get out of sync.
• Most modern languages support a structure.
• A structure is a data type
  • that stores a collection of potentially heterogeneous data.
  • members of fields are accessed by name.
  • Members can be either data or functions, but traditionally they are only data.

• struct identifier {
      type identifier[=value | {value}];
      ...
      type identifier[=value | {value}];
  };
      

• Example:

  • struct WordT {
         string word; 
         size_t count{0};
    };
            

  • This declares a new type, WordT.
  • This type can be use ANYWHERE a basic type can be used.
    • variable declarations
    • arguments and return types of functions.
    • Fields in other structures
• Declaring variables
  • WordT aWord;
  • WordT words[];
  • WordT avar{field1[field2, field3 ...]}; //fields in order
  • WordT avar{.fieldname = value};
  • And others, see this page
• The type does not allocate memory until a variable of that type is declared.
• Accessing members
  • use . notation.
  • aWord.word = "hello"
  • aWord.count++;
• No direct
  • I/O unless you tell it how.
  • Math unless you tell it how.
  • Comparison unless you tell it how.