Records

• The second of a user defined data type
  • If you don't know the first, you should probably review enumerated types.
• Also a structured data type.
• A record is a collection of related data.
  • Drivers license.
  • Everything about a polynomial
• Declared

  • 
    struct name {
        type name;
        type name;
    };
      

  • 
    struct imag {
        float real_part;
        float imag_part;
    };
         

  • There are other ways to abuse this:

    
    struct name {
         type name;
    } name1,name2;
         

    • In this case, name1 and name2 are variables of this type.
  • The types in the fields are any valid data type.
• Usage:
  • Declaring a struct normally does not declare a variable, it only defines what the variable will look like.
  • variables of the new type are declared as variables of other types.

  • 
    imag x,y;
          

    declares two variables of type imag.
  • Fields are dereferenced using a member selector.

  • 
    x.real_part = 5.3;
    y.imag_part = 2.7;
    

    sets the real and imaginary parts of the structure x.
• Things you can and can't do: (assume the declarations above)
  • x = y is ok
  • if ( x > y) // is not ok How are imaginary numbers compared
  • x = y + 1 // is not ok
  • cout << x //not ok, how should it be printed?
  • read_in_imag(imag & x) // ok
  • imag imag_add(imag x, imag y) { // fine.
• A heirarchial record
  • Is just a record, with another record as a field.

    
    struct address_rec {
        int    house_number;
        string stree_address;
        string city;
        string state;
    }
    
    struct telephone_rec {
        int area_code;
        int exchange;
        int local_number;
    }
    
    struct student_rec {
        string name;
        address_rec address;
        telephone_rec phone;
    }
        
     
    
    student_rec student;
    
        student.name = "Dan";
        student.address.city = "edinboro";
        student.phone.area_code = 814;