c++——模板中的非类型参数

Myth丶恋晨 2022-12-02 10:58 184阅读 0赞

\#\#\#在函数模板中使用非类型参数

#include<iostream>
    using namespace std;
    //在函数模板中使用非类型参数
    template<class T>void Swap(T &a, T &b);
    template<typename T, unsigned N>void Swap(T (&a)[N],T (&b)[N]);
    
    template<typename T, unsigned N>void printArray(T (&arr)[N]);
    
    int main(){ 
    	int m = 10, n = 90;
    	Swap(m,n);
    	cout << "m = " << m << ", n = " << n << endl;
    
    	int a[5] = {  1, 2, 3, 4, 5 };
    	int b[5] = {  10, 20, 30, 40, 50 };
    	Swap(a, b);
    	printArray(a);
    	printArray(b);
    	return 0;
    
    }
    
    template<class T> void Swap(T &a,T &b){ 
    	T temp = a;
    	a = b;
    	b = temp;
    }
    
    template<class T, unsigned N> void Swap(T (&a)[N],T (&b)[N]){ 
    	T temp;
    	for (int i = 0; i < N;i++){ 
    		temp = a[i]; 
    		a[i] = b[i];
    		b[i] = temp;
    	}
    }
    
    template<typename T, unsigned N>void printArray(T (&arr)[N]){ 
    	for (int i = 0; i < N;i++){ 
    		if (i == N-1){ 
    			cout << arr[i] << endl;
    		}
    		else{ 
    			cout << arr[i] << ", ";
    		}
    	}
    
    }

--------------------

\#\#\#\#\#在类模板中使用非类型参数

#include<iostream>
    #include<cstring>
    #include<cstdlib>
    using namespace std;
    
    //动态数组实现，在类模板中使用非类型参数
    template<typename T,int N>
    class Array{ 
    public:
    	Array();
    	~Array();
    public:
    	T & operator[](int i);//重载下标运算符
    	int length() const{  return m_length; }//获取数组长度
    	bool capacity(int n);//是否可改变数组容量
    private:
    	int m_length;//数组当前长度
    	int m_capacity;//当前内存容量
    	T *m_p;//指向数组内存的指针
    };
    
    template<typename T,int N>
    Array<T, N>::Array(){ 
    	m_p = new T[N];
    	m_capacity = m_length = N;
    }
    
    template<typename T,int N>
    Array<T, N>::~Array(){ 
    	delete[] m_p;
    }
    
    template<typename T,int N>
    T & Array<T, N>::operator[](int i){ 
    	if (i<0||i>=m_length){ 
    		cout << "Exception:Array index out of bounds!" << endl;
    	}
    	return m_p[i];
    }
    
    template<typename T,int N>
    bool Array<T, N>:: capacity(int n){ 
    	if (n>0){ 
    		int len = m_length + n;
    		if (len<=m_capacity){ 
    			m_length = len;
    			return true;
    		}
    		else{ 
    			T *pTemp = new T[m_length + 2 * n*sizeof(T)];
    			if (NULL==pTemp){ 
    				cout << "Exception: Failed to allocate memory!";
    				return false;
    			}
    			else{  
    				memcpy(pTemp,m_p,m_length*sizeof(T));
    				delete[] m_p;
    				m_p = pTemp;
    				m_capacity = m_length = len;
    			}
    		}
    	}
    	else{ 
    		int len = m_length - abs(n);
    		if (len<0){ 
    			cout << "Exception:Array length is too small!" << endl;
    			return false;
    		}
    		else{ 
    			m_length = len;
    			return true;
    		}
    	}
    }
    
    int main(){ 
    	Array<int, 5> arr;
    
    	for (int i = 0, len = arr.length(); i < len;i++){ 
    		arr[i] = 2 * i;
    	}
    
    	cout << "first print:" << endl;
    	for (int i = 0, len = arr.length(); i < len;i++){ 
    		cout << arr[i] << " ";
    	}
    	cout << endl;
    
    	//扩大容量为增加的元素赋值
    	arr.capacity(8);
    	for (int i = 5, len = arr.length(); i < len;i++){ 
    		arr[i] = 2 * i;
    	}
    
    	cout << endl;
    	cout << "second print:" << endl;
    	for (int i = 0, len = arr.length(); i < len;i++){ 
    		cout << arr[i] << " ";
    	}
    	cout << endl;
    
    	arr.capacity(-4);
    	cout << "third print: " << endl;
    	for (int i = 0, len = arr.length(); i < len; i++){ 
    		cout << arr[i] << " ";
    	}
    	cout << endl;
    
    	return 0;
    }