最近在看數(shù)據(jù)結(jié)構(gòu)方面的書籍，遇到了泛型編程方面的問題，以前遇到的泛型編程問題不多，大多數(shù)也已經(jīng)遺忘，于是打算重新?lián)炱饋?。下面一段關(guān)于泛型編程的定義摘抄于百度百科，應(yīng)該能概括什么事泛型編程。
泛型編程讓你編寫完全一般化并可重復(fù)使用的算法，其效率與針對(duì)某特定數(shù)據(jù)類型而設(shè)計(jì)的算法相同。泛型編程的代表作品STL是一種高效、泛型、可交互操作的軟件組件。所謂泛型（Genericity)，是指具有在多種數(shù)據(jù)類型上皆可操作的含意，與模板有些相似。STL巨大，而且可以擴(kuò)充，它包含很多計(jì)算機(jī)基本算法和數(shù)據(jù)結(jié)構(gòu)，而且將算法與數(shù)據(jù)結(jié)構(gòu)完全分離，其中算法是泛型的，不與任何特定數(shù)據(jù)結(jié)構(gòu)或?qū)ο箢愋拖翟谝黄?。STL以迭代器 (Iterators)和容器(Containers)為基礎(chǔ)，是一種泛型算法(Generic Algorithms)庫，容器的存在使這些算法有東西可以操作。STL包含各種泛型算法(algorithms)、泛型指針(iterators)、泛型容器(containers)以及函數(shù)對(duì)象(function objects)。STL并非只是一些有用組件的集合，它是描述軟件組件抽象需求條件的一個(gè)正規(guī)而有條理的架構(gòu)。
上面的概括只是從理論上解釋了什么是泛型，可是看過后還是不知道怎么使用泛型，于是乎筆者找到了STL中定義的頭文件，下面就一步一步解開泛型的秘密。
由于原版的STL中很多類的套嵌，不便于解釋，所以簡化了STL，以下以vector容器為例：
文件名：vector.h
1: template //模板定義了Object類型，在使用的時(shí)候可以以任何類型代替此類型
2: class vector
3: {
4: public:
5: explicit vector( int initSize = 0 ) : theSize( initSize ), theCapacity( initSize + SPARE_CAPACITY )//重點(diǎn)注意構(gòu)造函數(shù)的定義，構(gòu)造函數(shù)支持兩種方式初始化vector容器,這下知道怎么用vector了吧
6: { objects = new Object[ theCapacity ]; }
7: vector( const vector & rhs ) : objects( NULL )
8: { operator=( rhs ); }
9: ~vector( )
10: { delete [ ] objects; }
11:
12: bool empty( ) const
13: { return size( ) == 0; }
14: int size( ) const
15: { return theSize; }
16: int capacity( ) const
17: { return theCapacity; }
18:
19: Object & operator[]( int index )
20: {
21: #ifndef NO_CHECK
22: if( index < 0 || index >= size( ) )
23: throw ArrayIndexOutOfBoundsException( index, size( ) );
24: #endif
25: return objects[ index ];
26: }
27:
28: const Object & operator[]( int index ) const
29: {
30: #ifndef NO_CHECK
31: if( index < 0 || index >= size( ) )
32: throw ArrayIndexOutOfBoundsException( index, size( ) );
33: #endif
34: return objects[ index ];
35: }
36:
37: const vector & operator = ( const vector & rhs );
38: void resize( int newSize );
39: void reserve( int newCapacity );
40:
41: // Stacky stuff
42: void push_back( const Object & x );
43: void pop_back( );
44: const Object & back ( ) const;
45:
46: // Iterator stuff: not bounds checked
47: typedef Object * iterator;
48: typedef const Object * const_iterator;
49:
50: iterator begin( )
51: { return &objects[ 0 ]; }
52: const_iterator begin( ) const
53: { return &objects[ 0 ]; }
54: iterator end( )
55: { return &objects[ size( ) ]; }
56: const_iterator end( ) const
57: { return &objects[ size( ) ]; }
58:
59: enum { SPARE_CAPACITY = 16 };
60:
61: private:
62: int theSize;
63: int theCapacity;
64: Object * objects;
65: };
文件名：vector.cpp
1: template //模板定義了Object類型，在使用的時(shí)候可以以任何類型代替此類型
2: const vector & vector::operator=( const vector & rhs )//重載賦值操作符
3: {
4: if( this != &rhs )//優(yōu)化a=a的情況
5: {
6: delete [ ] objects;
7: theSize = rhs.size( );
8: theCapacity = rhs.theCapacity;
9:
10: objects = new Object[ capacity( ) ];
11: for( int k = 0; k < size( ); k++ )
12: objects[ k ] = rhs.objects[ k ];
13: }
14: return *this;
15: }
16:
17: //以下為一些常用操作函數(shù)的定義
18:
19: template
20: void vector::resize( int newSize )
21: {
22: if( newSize > theCapacity )
23: reserve( newSize * 2 );
24: theSize = newSize;
25: }
26:
27:
28: template
29: void vector::reserve( int newCapacity )
30: {
31: Object *oldArray = objects;
32:
33: int numToCopy = newCapacity < theSize ? newCapacity : theSize;
34: newCapacity += SPARE_CAPACITY;
35:
36: objects = new Object[ newCapacity ];
37: for( int k = 0; k < numToCopy; k++ )
38: objects[ k ] = oldArray[ k ];
39:
40: theSize = numToCopy;
41: theCapacity = newCapacity;
42:
43: delete [ ] oldArray;
44: }
45:
46:
47: template
48: void vector::push_back( const Object & x )
49: {
50: if( theSize == theCapacity )
51: reserve( 2 * theCapacity + 1 );
52: objects[ theSize++ ] = x;
53: }
54:
55:
56: template
57: void vector::pop_back( )
58: {
59: if( empty( ) )
60: throw UnderflowException( "Cannot call pop_back on empty vector" );
61: theSize--;
62: }
63:
64:
65: template
66: const Object & vector::back( ) const
67: {
68: if( empty( ) )
69: throw UnderflowException( "Cannot call back on empty vector" );
70: return objects[ theSize - 1 ];
71: }