Records C++ Structs

Июль 23, 2022

Содержание

2. What to do with records? Declaring records Accessing records Accessing the field of a record What
3. Records Recall that elements of arrays must all be of the same type In some situations,
4. Records RECORDS are used to group related components of different types Components of the record are
5. Records C++ struct structured data type fixed number of components elements accessed by name, not by
6. Declaring struct Variables Given Declare : struct part_struct { char descrip [31], part_num [11]; float unit_price;
7. Accessing Components Use the name of the record the name of the member separated by a
8. Aggregate Operations with Structures Recall that arrays had none (except reference parameter) Structures DO have aggregate
9. Aggregate Operations with Structures Limitations on aggregate operations no I/O no arithmetic operations no comparisons cout
10. Aggregate Operations with Structures struct variables must be compared member-wise. To compare the values of student
11. Input/Output There are no aggregate input/output operations on struct. Data in a struct variable must be
12. struct Variables and Functions A struct variable can be passed as a parameter either by value
13. Arrays of Records First declare a struct (such as part_struct) Then specify an array of that
14. Records with Arrays Example const int arraySize = 1000; struct listType { int elements[arraySize]; //array containing
15. Hierarchical Records records where at least one of the components is, itself, a record Example: struct
16. Choosing Data Structures Strive to group logical elements of a structure together calls for hierarchical structures
17. Testing and Debugging Hints Declaration of a struct type must end with a semicolon ; Be
18. Testing and Debugging When using an array in a struct, the index goes at the end
19. Testing and Debugging Process struct members separately … the only aggregate operations will be Assignment =
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Слайд 2

What to do with records?
Declaring records
Accessing records
Accessing the field of a

record
What is a union?
Can records be in arrays?

Слайд 3

Records
Recall that elements of arrays must all be of the same

type
In some situations, we wish to group elements of different types

scores : 85 79 92 57 68 80 . . .

0 1 2 3 4 5 98 99

Слайд 4

Records
RECORDS are used to group related components of different types
Components of

the record are called fields
In C++
record called a struct (structure)
fields called members

Слайд 5

Records
C++ struct
structured data type
fixed number of components
elements accessed by name, not

by index
components may be of different types

struct part_struct { char descrip [31], part_num [11]; float unit_price; int qty; };

Слайд 6

$Declaring struct Variables Given Declare : struct part_struct { char descrip$

Declaring struct Variables
Given
Declare :
struct part_struct { char descrip [31], part_num [11];

float unit_price; int qty; };

part_struct new_part, old_part;

Use struct name as a type.

Слайд 7

Accessing Components
Use the name of the record the name of the

member separated by a dot .
The dot is called the member selector

old_part.qty = 5;
cout << new_part.descrip;

Слайд 8

Aggregate Operations with Structures
Recall that arrays had none (except reference parameter)
Structures

DO have aggregate operators
assignment statement =
parameter (value or reference)
return a structure as a function type

Слайд 9

Aggregate Operations with Structures
Limitations on aggregate operations
no I/O
no arithmetic operations
no comparisons

cout << old_part; cin >> new_part;

old_part = new_part + old_part;

if (old_part < new_part) cout << ...;

Слайд 10

Aggregate Operations with Structures
struct variables must be compared member-wise.
To

compare the values of student and newStudent, you must compare them member-wise, as follows:
if(student.firstName == newStudent.firstName &&
student.lastName == newStudent.lastName) ...

Слайд 11

Input/Output
There are no aggregate input/output operations on struct.
Data in

a struct variable must be read one member at a time.
Contents of a struct must be written one member at a time.

Слайд 12

struct Variables and Functions
A struct variable can be passed as

a parameter either by value or by reference.
A function can return a value of the type struct
Note example program fragment

Слайд 13

Arrays of Records
First declare a struct (such as part_struct)
Then specify an

array of that type
Access elements of the array, elements of the struct

part_struct part_list [50];

for (x = 0; x <50; x++) cout << _______________________;

How do we print all the descrip fields?

part_list[x].descrip

Слайд 14

Records with Arrays
Example
const int arraySize = 1000;
struct listType
{
int elements[arraySize]; //array

containing the list
int listLength; //length of the list
}

See sample program

Слайд 15

Hierarchical Records
records where at least one of the components is, itself,

a record
Example:

struct inventory_struct { part_struct part; int qty_sold, re_order_qty; vendor_struct vendor; };

Слайд 16

Choosing Data Structures
Strive to group logical elements of a structure together
calls

for hierarchical structures
Push details of entities down to lower levels of the structure
Data Abstraction <=> separation of logical peoperties of a data type from its implementation

Слайд 17

Testing and Debugging Hints
Declaration of a struct type must end with

a semicolon ;
Be sure to specify the full member selector when referencing a component of a struct variable
don’t leave out the struct name

Слайд 18

Testing and Debugging
When using an array in a struct, the index

goes at the end student_rec.scores[x]
When using an array of struct, the index goes after the struct name parts_list[x].qty

Слайд 19

Testing and Debugging
Process struct members separately … the only aggregate operations

will be
Assignment =
Parameter passing void do_it (part_struct part);
Function return part_struct blanked_part ( );

Records C++ Structs

Содержание

What to do with records?Declaring recordsAccessing recordsAccessing the field of a

RecordsRecall that elements of arrays must all be of the same

RecordsRECORDS are used to group related components of different typesComponents of

RecordsC++ structstructured data typefixed number of componentselements accessed by name, not

Declaring struct VariablesGivenDeclare :struct part_struct { char descrip [31], part_num [11];

Accessing ComponentsUse the name of the record the name of the

Aggregate Operations with StructuresRecall that arrays had none (except reference parameter)Structures

Aggregate Operations with StructuresLimitations on aggregate operationsno I/O no arithmetic operationsno comparisons

Aggregate Operations with Structures struct variables must be compared member-wise. To

Input/Output There are no aggregate input/output operations on struct. Data in

struct Variables and Functions A struct variable can be passed as

Arrays of RecordsFirst declare a struct (such as part_struct)Then specify an

Records with ArraysExampleconst int arraySize = 1000;struct listType{ int elements[arraySize]; //array

Hierarchical Recordsrecords where at least one of the components is, itself,

Choosing Data StructuresStrive to group logical elements of a structure togethercalls

Testing and Debugging HintsDeclaration of a struct type must end with

Testing and DebuggingWhen using an array in a struct, the index

Testing and DebuggingProcess struct members separately … the only aggregate operations

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