61 lines
1020 B
C++
61 lines
1020 B
C++
/**
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* @file decltype.cpp
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* @brief g++ -o decltype decltype.cpp -std=c++11
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* @author 光城
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* @version v1
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* @date 2019-08-08
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*/
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#include <iostream>
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#include <vector>
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using namespace std;
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/**
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* 泛型编程中结合auto，用于追踪函数的返回值类型
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*/
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template <typename T>
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auto multiply(T x, T y)->decltype(x*y)
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{
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return x*y;
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}
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int main()
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{
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int nums[] = {1,2,3,4};
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vector<int> vec(nums,nums+4);
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vector<int>::iterator it;
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for(it=vec.begin();it!=vec.end();it++)
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cout<<*it<<" ";
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cout<<endl;
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using nullptr_t = decltype(nullptr);
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nullptr_t nu;
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int * p =NULL;
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if(p==nu)
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cout<<"NULL"<<endl;
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typedef decltype(vec.begin()) vectype;
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for(vectype i=vec.begin();i!=vec.end();i++)
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cout<<*i<<" ";
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cout<<endl;
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/**
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* 匿名结构体
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*/
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struct
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{
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int d ;
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double b;
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}anon_s;
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decltype(anon_s) as; // 定义了一个上面匿名的结构体
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cout<<multiply(11,2)<<endl;
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return 0;
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}
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