1 programming languages implementation of data structures cao hoaøng truï khoa coâng ngheä...

1

Programming Languages Implementation of Data

Structures

Cao Hoaøng Truï

Khoa Coâng Ngheä Thoâng TinÑaïi Hoïc Baùch Khoa TP. HCM

2

Contents

• Fundamentals

• Elementary data types

• Structured data types

• Subprograms

3

Fundamentals

• Data objects

• Data types

• Type specification and implementation

• Declaration

• Type checking, compatibility, and conversion

• Assignment and initialisation

4

Data Objects

• A run-time grouping of one or more pieces of data

• A container for data values

• Block of storage

• Programmer-defined and system-defined

• Lifetime

• Variables and constants

5

Fundamentals

• Data objects

• Data types


• Declaration



6

Data Types

• A class of objects having the same properties

• Primitive data types

7

Fundamentals

• Data objects

• Data types


• Declaration



8

Specification

• Attributes

• Values

• Operations:op_name: arg_type x arg_type x … result_type x result_type x …

9

Examples: Arrays

• Attributes:

number of dimensions subscript range for each dimension data types of the components

• Values: valid values for the components

• Operations: subscripting, creating, accessing attributes

10

Implementation

• Storage representation

• Operation definitions:

hardware operations subprograms in-line codes

11

Fundamentals

• Data objects

• Data types


• Declaration



12

Declaration

• To provide information about data objects:

number and type name and position lifetime constant and initialised value

13

Declaration

• Data type declaration:

by namevar A: integer

by specification

var A: array [1..20] of integer

14

Declaration

• Operation declaration:

argument number, order, data types result number, order, data types

function FOO(X: integer; Y: real) : real;

FOO: integer x real real

15

Declaration

• Purposes:

choice of storage representations storage management generic operations type checking

16

Fundamentals

• Data objects

• Data types


• Declaration



17

Type Checking

• Checking if each operation receives the proper number of arguments of the proper data types

• Dynamic (run time) vs. static (compile time) type checking

18

Type Checking

• Dynamic type checking:

no declarations required types of data objects may change as needed programmers have no concerns about data types difficult to debug and remove type errors extra storage required for keeping type information reduction of execution speed

19

Type Compatibility

• T1 and T2 are compatible if data objects of type T1 can occur in the positions of data objects of type T2, and vice versa: name or structural equivalence

type VECT1: array [1..10] of real; VECT2: array [1..10] of real;

var X, Y: VECT1; Z: VECT2;

Y := X; Z := Y;

20

Type Compatibility

• Name equivalence:

no anonymous types allowed global type definitions used

var X: array [1..10] of real;

21

Type Compatibility

• Structural equivalence:

difficult to define static type checking compromised cost to check

type METERS = integer; LITERS = integer;var LEN: METERS;VOL: LITERS;

LEN + VOL

22

Type Conversion

• When types are mismatched:

type error type conversion (coercion)

var A: integer; int I; B, C: real; unsigned U;

float F;C := A + BI = - 1; U = 1; F = U I; /* I = - 1 65535 */

23

Fundamentals

• Data objects

• Data types


• Declaration



24

Assignment

• Basic operation for changing values of data objects

• Specification:

:= : type1 x type2 void = : type1 x type2 type3

Z := X + Y Z = X + (Y = W 2)

A = B = C

25

Initialisation

• To set a value in the storage of an data object

• Un-initialised data object

• Explicit and implicit initialisation

26

Programming Languages Implementation of Data

Structures

Cao Hoaøng Truï

Khoa Coâng Ngheä Thoâng TinÑaïi Hoïc Baùch Khoa TP. HCM

27

Contents

• Fundamentals



• Subprograms

28

Elementary Data Types

• Numeric data types

• Enumerations

• Booleans

• Characters

29

Numeric Data Types

• Integers

• Subranges

• Floating-point real numbers

• Fixed-point real numbers

• Complex numbers

• Rational numbers

30

Integers

2 bytes

4 bytes

-32768 32768

-65536 65536

31

Subranges

var A: 1..10

• Smaller storage requirements fewer bits than a general integer software-simulated operations

• Better type checking

32

Floating-Point Real Numbers

exponent

mantissaSign bit for

mantissa

Sign bit for exponent

6.7510 = 110.112 = 0.110112 x 23 = 0.110112 x 00112

110110011

00

33

Fixed-Point Real Numbers

integer part fractional part

Sign bit

6.7510 = 110.112

11

1100

34

Complex Numbers

real part

imaginary part

35

Rational Numbers

• To avoid roundoff and truncation

• Pairs of integers of unbounded length

Sign bit

numerator

denominator

36



• Enumerations

• Booleans

• Characters

37

Enumerations

type DEGREE = (bachelor, master, doctor)

0 1 2

38



• Enumerations

• Booleans

• Characters

39

Booleans

• A particular bit

• Zero/non-zero value

1 byte

40



• Enumerations

• Booleans

• Characters

41

Characters

1 byte

2 byte

42

Contents

• Fundamentals



• Subprograms

43

Structured Data Types

• Fundamentals• Vectors and arrays• Records• Character strings• Pointers• Sets• Files

44

Fundamentals

• Specification

• Implementation

• Type checking

45

Specification

• Attributes: Number of components Type of each component Names for selecting components Maximum number of components Organization of components

46

Specification

• Operations: Component selection (random/sequential) Whole-data-structure operations Insertion/deletion Creation/destruction

47

Implementation

• Storage representation:

Decriptor

Component

Component

Decriptor

Component

Component

Sequential

Linked

48

Implementation

• Selection operation:

Sequential base-address-plus-offset Linked pointer following

49

Implementation

• Storage management:

Garbage

Dangling Referenc

es

objectobject

50

Type Checking

var A: array [1..10] of real;

• Existence of a selected component:

A[I]

• Type of a selected component:

A[2].link.item

51


• Fundamentals• Vectors and arrays• Records• Character strings

• Pointers• Sets• Files

52

Vectors

Vector

LB

UB

Integer

E

Base address

Component size A[LB

]A[LB + 1]

A[UB]

var A: array [1..10] of integer;

loc A[I] = + D + (I - LB) x E

packed/unpacked storage

53

Matrix

var A: array [1..2, -1..1] of real;

1

2

-1 0 1-1

0

1

1 2

row-major order

column-major order

54

Multidimensional Arrays

var A: array [LB1..UB1, LB2..UB2, …, LBn..UBn] of real;• Row-major order:

var A: array [LB1..UB1] of array [LB2..UB2, …, LBn..UBn] of real;

• Column-major order:

var A: array [LBn..UBn] of array [LB1..UB1, …, LBn-1..Ubn-1] of real;

55

MatrixMatrix

LB1

UB1

LB2

UB2

Real

E

Base address

Component size

A[1, -1]A[1, 0]

var A: array [1..2, -1..1] of real;

loc A[I, J] = + D + (I - LB1) x S

+ (J - LB2) x E

S = (UB2 - LB2 + 1) x E

loc A[I, J] = + K + I x S + J x E

K = D - LB1 x S - LB2 x E

A[1, 1]

A[2, -1]A[2, 0]

A[2, 1]

56




57

Records

• Heterogeneous components

• Symbolic names for components

var EMPLOYEE: recordID: integer;AGE: integer;DEPT: string;SALARY: real;end

58

Records

22901

2901.10

Base address

ID

loc R.I = + j=1, I-1(size of R.j)

27

“IT”

AGE

DEPT

SALARY

computed during compile time

59

Variant Recordstype PAY_TYPE = (MONTHLY, HOURLY)

var EMPLOYEE: recordID: integer;AGE: integer;DEPT: string;case PAY_CLASS: PAY_TYPE ofMONTHLY: (MONTH_RATE: real;START_DATE: integer);HOURLY: (HOUR_RATE: real;REG_HOURS: integer;OVERTIME: integer)end

60

Variant Records

22901 ID

27

“IT”

AGE

DEPT

PAY_CLASSHOUR_RATE

REG_HOURSOVERTIME

ID

AGE

DEPT

PAY_CLASS

MONTH_RATE

START_DATE

Unused

61

Variant Records

• Dynamic tag checking

• No checking

62




63

Character Strings

R E L A

T I V I

T Y

• Fixed declared length:

64

Character Strings

12

8 E I

N S T E

I N

• Variable length with declared bound:

Maximum lengthCurrent length

65

Character Strings

• Unbounded length:

Current length

8

IE SN

ET NI

66

Character Strings

• Concatenation

• Relational operations

• Substring selection (by character-position/pattern matching)

• Input-output formatting

67




68

Pointers

• Referencing data objects of a single type

type VECT = array [1..20] of real;

var P: VECT;

• Referencing data objects of any type

69

Pointers

Object

d

0

d

Object

d

0

d

Absolute address

Relative address

70

Pointers

• Absolute address: fast access difficult storage management

• Relative address: slower access simpler storage management

71

Pointers

• List:

type ELEMENT = record HEAD: integer;TAIL: ELEMENT

end

var P: ELEMENT

P

72




73

Sets

• Membership test

• Element insertion/deletion

• Union, intersection, difference

74

Sets

var S: set of (mon, tue, wed, thu, fri, sat, sun);

• Bit-string representation:

mon tue wed thu fri sat sun

[mon, wed, fri]

1 0 1 0 1 0 0

[mon, tue, wed]

1 1 1 0 0 0 0

[mon, wed] 1 0 1 0 0 0 0

75

Sets

• Hash-coded representation: for large domain size each set is represented by a storage block each element has a hash address in that block

76




77

Files

• Represented on a secondary storage device (disk/tape)

• Much larger than data structures of other types

• Lifetime is longer than that of the program creating it

78

Files

• Sequential files

• Text files

• Direct-access files

• Indexed sequential files

79

Files

• Open

• Read

• Write

• End-of-file test

80

Contents

• Fundamentals



• Subprograms

81

Subprograms

• Abstract operations: name arguments results action

• Data objects

82

Subprograms

function FOO(X: real; Y: integer): real; var A: array [1..10] of real;

N: integer;begin

…

N := Y + 1; X := A[N]2; …

end;

83

Subprograms

• Code segment (static part)

• Activation record (dynamic part): parameters function results local variables

84

Subprograms

PrologueFOO

Code segment Activation record

Epilogue

Statement executable codes

Return point and system data

X

Y

A

N

85

Subprograms

Code segment

Activation record 1

Activation record 2

Activation record N

1st call

2nd call

N-th call

86

Exercises

• Consider the following piece of program: program P;

var A: 1..10; N: integer;begin…

read(N);A := N + 1;…end;

Where is type checking?

Can it be done statically?

Can it be done dynamically and

how?

87

Exercises

• Illustrate the storage representation of A: array [0..1, 1..2] of integer using the column-major order. Give the accessing formula for computing the location of A[I, J], supposing that the size of an integer is 2 bytes.

1 programming languages implementation of data structures cao hoaøng truï khoa coâng ngheä...

Documents

types of data objects

type x slide

type checking checking

data values

dimension data types

data types difficult

pieces of data

dynamic type checking