四、模板编程——学习C++类库的编程基础
一、函数模板
模板不能在一个文件中定义在一个文件中使用。
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模板代码调用之前，一定要看到模板定义的地方，这样的话，目标才能够进行正常的实例化，产生能够被编译器编译的代码
所以，模板代码都是放在头文件当中，然后在源文件当中直接进行#include包含
模板的非类型参数
都是常量，只能使用，不能修改
templete//非类型参数
void sort(T *arr){
//排序
for(int i=0;iarr[j+1]){
int tmp=arr[j];
arr[j]=arr[j+1];
arr[j+11]=tmp;
}
}
}
}
int main(){
int arr[]={12,455,456,13,54,43};
const int size=sizeof（arr）/sizeof(arr[0]);
sort(arr);//在这里使用非参数列表，后面的size是const的类型
}
二、类模板
构造和析构函数名不用加
template
class SeqStackT
{
public:
SeqStackT(int size = 10)
:_top(-1),
_size(size),
_pstack(new T[size]) { }
SeqStackT(const SeqStackT& src)
:_top(src._top),
_size(src._top) {
cout << this << "SeqStackT<>(const SeqStack& src)" << endl;
_pstack = new T[src._size];
for (int i = 0; i <= src._top; i++) {
_pstack[i] = src._pstack[i];
}
}
~SeqStackT() {
cout << this << "~SeqStack()" << endl;
delete[] _pstack;
_pstack = nullptr;
}
SeqStackT& operator=(const SeqStackT& src) {
cout << "operator=" << endl;
//防止自赋值
if (this == &src) {
return *this;
}
delete[] _pstack;//需要释放掉自身占用的外部资源
_pstack = new T[src._size];
for (int i = 0; i <= src._top; i++) {
_pstack[i] = src._pstack[i];
}
_top = src._top;
_size = src._size;
return *this;
}
void push(int val) {
if (full()) {
resize();
}
_pstack[++_top] = val;
}
void pop() {
if (empty()) {
return;
}
--_top;
}
int top() {
return _pstack[_top];
}
bool empty() { return _top == -1; }
bool full() { return _top == _size - 1; }
private:
T* _pstack;
int _top;
int _size;
void resize() {
int* ptmp = new T[_size * 2];
for (int i = 0; i < _size; i++) {
ptmp[i] = _pstack[i];
}
delete[] _pstack;
_pstack = ptmp;
_size *= 2;
}
};
三、实现vector
//
// Created by on 2022-05-15 20:33.
// Description:
//
#ifndef C___VECTORT_H
#define C___VECTORT_H
using namespace std;
template
class VectorT {
public:
VectorT(int size = 10) {
_first=new T[size];
_last=_first;
_end=_first+size;
}
~VectorT() {
delete[] _first;
_first = _last = _end = nullptr;
}
VectorT(const VectorT &src) {
int size = src._end - src._first;
_first = new T[size];
int len = src._last - src._first;
for (int i = 0; i < len; i++) {
_first[i] = src._first[i];
}
_last = _first + len;
_end = _first + size;
}
VectorT &operator=(const VectorT &src) {
if (src == *this) {
return *this;
}
delete[] _first;
int size = src._end - src._first;
_first = new T[size];
int len = src._last - src._first;
for (int i = 0; i < len; i++) {
_first[i] = src._first[i];
}
_last = _first + len;
_end = _first + size;
return *this;
}
void push_back(T val) {
if (full()) {
expend();
}
*_last++ = val;
}
void pop_back() {
if (empty()) { return; }
_last--;
}
T back() const{
return *(_last - 1);
}
bool full() const{
return _last == _end;
}
bool empty() const{
return _first == _last;
}
int size() const{
return _last - _first;
}
private:
T *_first;//表示vector起始位置
T *_last;//表示vector定义元素的末尾
T *_end;//表示vector的末尾
void expend() {//size扩大两倍
int size = _end - _first;
T *ptmp = new T[size * 2];
for (int i = 0; i < size; i++) {
ptmp[i] = _first[i];
}
delete[] _first;
_first = ptmp;
_last = _first + size;
_end = _first + (2 * size);
}
};
#endif //C___VECTORT_H
//实现
int main() {
VectorT vec;
for(int i=0;i<15;i++){
vec.push_back(rand()%100);
}
while (!vec.empty()){
cout< 空间配置器Allocator
使用空间配置器实现vector容器：
//
// Created by on 2022-05-15 21:29.
// Description: AllocatorT.h
//
#include
/**
* 定义容器的空间配置器，和C++标准库的allocator的实现一致
* @tparam T
*/
template
struct AllocatorT {
T *allocate(size_t size) {//负责内存开辟
return (T *) malloc(sizeof(T) * size);
}
void deallocate(void *p) {//负责内存释放
free(p);
}
void construct(T *p, const T &val) {//负责对象构造
new(p) T(val);//定位new
}
void destory(T *p) {//负责对象析构
p->~T();//析构函数
}
};
vector类：
//
// Created by on 2022-05-15 21:29.
// Description: VectorT.h
//
#include "AllocatorT.h"
using namespace std;
/**
* 容器底层内存开辟，内存释放，对象构造和析构都通过allocator实现
* @tparam T
* @tparam Alloc
*/
template >
class VectorT {
public:
VectorT(int size = 10) {
// _first=new T[size];
_first = _alloctor.allocate(size);
_last = _first;
_end = _first + size;
}
~VectorT() {
// delete[] _first;
//使用allocator对vector逐个删除
for (T *p = _first; p != _last; p++) {
_alloctor.destory(p);
}
_alloctor.deallocate(_first);
_first = _last = _end = nullptr;
}
VectorT(const VectorT &src) {
int size = src._end - src._first;
// _first = new T[size];
_first = _alloctor.allocate(size);
int len = src._last - src._first;
for (int i = 0; i < len; i++) {
// _first[i] = src._first[i];
_alloctor.contruct(_first + 1, src._first[i]);
}
_last = _first + len;
_end = _first + size;
}
VectorT &operator=(const VectorT &src) {
if (src == *this) {
return *this;
}
//delete[] _first;
for (T *p = _first; p != _last; p++) {
_alloctor.destory(p);
}
_alloctor.deallocate(_first);
int size = src._end - src._first;
_first = new T[size];
int len = src._last - src._first;
for (int i = 0; i < len; i++) {
// _first[i] = src._first[i];
_alloctor.contruct(_first + 1, src._first[i]);
}
_last = _first + len;
_end = _first + size;
return *this;
}
void push_back(T val) {
if (full()) {
expend();
}
//*_last++ = val;
_alloctor.construct(_last, val);
_last++;
}
void pop_back() {
if (empty()) { return; }
--_last;
_alloctor.destory(_last);
}
T back() const {
return *(_last - 1);
}
bool full() const {
return _last == _end;
}
bool empty() const {
return _first == _last;
}
int size() const {
return _last - _first;
}
private:
T *_first;//表示vector起始位置
T *_last;//表示vector定义元素的末尾
T *_end;//表示vector的末尾
Alloc _alloctor;//负责内存管理
void expend() {//size扩大两倍
int size = _end - _first;
// T *ptmp = new T[size * 2];
T *ptmp = _alloctor.allocate(2 * size);
for (int i = 0; i < size; i++) {
//ptmp[i] = _first[i];
_alloctor.construct(ptmp + i, _first[i]);
}
//delete[] _first;
for (T *p = _first; p != _last; p++) {
_alloctor.destory(p);
}
_alloctor.deallocate(_first);
_first = ptmp;
_last = _first + size;
_end = _first + (2 * size);
}
};
main函数实现：
#include
#include "header/vectorT.h"
using namespace std;
struct Test {//测试类，只测试三种函数
Test() {
cout << "Test()" << endl;
}
Test(const Test& src){
cout<<"Test(const Test& src)"< vec;
vec.push_back(t1);
vec.push_back(t2);
vec.push_back(t3);
cout<<"______________________"< 文章名称：四、模板编程——学习C++类库的编程基础
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