9 장 추상 데이터 타입 및 모듈(Abstract Data Type & Module)

9.1 캡슐화 및 추상 데이터 타입(Encapsulation and Abstract Data Types)

추상화 (Abstraction) The concept of abstraction is fundamental in

programming

Control abstraction control structures Procedures

Data abstraction data types

프로시져 사용 예제 typedef struct {

float re,im; } COMPLEX;

COMPLEX add( COMPLEX x, y) { . . . }COMPLEX subtract( COMPLEX x, y) { . . . }COMPLEX multiply( COMPLEX x, y) { . . . }COMPLEX divide( COMPLEX x, y) { . . . } COMPLEX a, b, c;c = add(a,b);

프로시져 사용의 문제점 Any procedures(operations) can use COMPLEX data type

Direct access of fields of COMPLEX variables ?

No separation of interface and implementation

캡슐화 (Encapsulation) Original motivation

Large programs have two special needs: Some means of organization, other than simply division into

subprograms Separate compilation units

Obvious solution Unit abstraction or encapsulations a grouping of logically related subprograms with data

types

추상 데이터 타입 Basic idea

Collections of data(variables) and operations(procedures) Originated from Simula-67

Encapsulation define a data type with operations data + operations restrict the use of the type to the defined operations

추상 데이터 타입 연산 (메쏘드 )

데이터

클라이언트

추상 데이터 타입의 장점 수정 용이성

구현에 독립적인 인터페이스

재사용가능성 표준 인터페이스로 다른 프로그램에서도 재사용

보안성 구현의 세부사항을 프로그램 다른 부분에서 접근 금지

추상 데이터 타입의 예 Module in Modula-2

Package in Ada

Class in Java, and C++

추상 데이터 타입의 수학적 의미 (S, Op) where

S is a set of data Op is a set of operations.

프로그래밍 단위 Procedural languages

Procedures

Languages with ADT Modules in Modula-2, Package in Ada

Object-oriented languages Class

모듈을 이용한 프로그래밍 var s, t : stack;begin

s := newstack;t := newstack;push(10,s);. . .

end.

type stack; function pop(s:stack) : integer; procedure push(a: integer; s:stack); function newstack : stack;

representation of stacks (type stack) . . . initialization (newstack) . . . procedure bodies (pop, push)

Module StackManager

정보 은닉 (Information Hiding) 구현의 세부 사항을 정의에서 분리 구현의 세부 사항은 프로그램 다른 부분에서 접근 금지

모듈 (Module) Role

A collection of data(variables) and operations(procedures)

Interface(definition) part public part can be accessed outside of the package since it is public

Implementation part private part an implementation detail cann't be accessed outside of the ADT

클래스를 타입 이름으로 In C++Stack s, t;s.push(7);s.push(8);

In JavaStack s, t;s = new Stack( );t = new Stack( );s.push(7);

class Stack { public:

Stack();void push(int a);int pop();

private representation of stacks . . . initialization (Stack) . . . procedure bodies (pop, push)

비교 Procedures

data type and operation are defined separately implementation details are accessible throughout program

ADT (Modules, Packages) define data type with its operations interface and implementation implementation is hidden accss is checked

비교 Class

class is a defined type as data and operations

interface and implementation implementation is hidden accss is checked

object an instance of a class

inheritance

9.2 프로그램 설계

프로그램 설계 Program design

discover the right object, right module Decide which types you want; Provide a full set of operations for each type

Class and modules Formulate the structure of a program

모듈 var s, t : stack;begin

s := newstack;t := newstack;push(10,s);push(10,s);. . .

end.

type stack; function pop(s:stack) : integer; procedure push(a: integer; s:stack); function newstack : stack; type stack = ^ rep

rep = recordelements: array[0..100] of integer;top : integer;

end; (type stack)

function newstack : stack; var s: stack;begin new(s); s^.top :=0; newstack :=send; procedure bodies (pop, push)

Module StackManager

Ada 의 패키지 Ada 에서 제공하는 ADT

Package

Package 구성 Package specification

the interface Package Body

implementation of the entities named in the specification

Ada 의 패키지 예제package COMPLEX_TYPE is

type COMPLEX is private;I: constant COMPLEX;function + (X, Y: COMPLEX) return COMPLEX;function - (X, Y: COMPLEX) return COMPLEX;function * (X, Y: COMPLEX) return COMPLEX;function / (X, Y: COMPLEX) return COMPLEX;function +(X:float; Y:COMPLEX) return COMPLEX; function - (X: COMPLEX) return COMPLEX;,function RE (X: COMPLEX) return float;function IM (X: COMPLEX) return float;

privatetype COMPLEX is record re, im : float := 0.0; end recordI : contant COMPLEX := (0.0, 1.0);

end COMPLEX_TYPE;

Ada 의 패키지 예제package body COMPLEX_TYPE is

function +(X,Y:COMPLEX) return COMPLEX isbegin

return(X.RE+Y.RE, X.IM+Y.IM);end;function RE(X:COMPLEX) return float isbegin return X.RE; end;function +(X:float; Y:COMPLEX) return COMPLEX isbeginreturn(X+Y.RE, Y.IM);end; ... others ...

end COMPLEX_TYPE;

Ada 의 패키지 사용 declare

use COMPLEX_TYPE; X,Y: COMPLEX;Z: COMPLEX := 1.5 + 2.5*I;

beginX := 2.5 + 3.5*I; Y := X + Z;Z := RE(Z) + IM(X)*I;if X = Y then X:= Y+Z;else X:= Y*Z; end if;

end

9.3 매개변수를 갖는 추상 데이터 타입

매개변수를 갖는 추상 데이터 타입 Procedure 혹은 function 이 적용될 수 있는 데이터

타입의 확장

타입을 parameter 로 받는 메커니즘 이용 Ada: Generic C++: Template

예제template <class T> class Stack {

T* v;T* p;int sz;

public:Stack(int s) { v=p=new T[sz=s];}~Stack( ) { delete[] v;}void push(T a) { p++ = a;}T pop( ) { return *--p;}Int size( ) { return p-v;}

}Stack<char> sc(100);Stack<int> si(100);Stack<point> sp(100);