1、編寫(xiě)一個(gè)類(lèi)令其檢查兩個(gè)值是否相同，替換掉某個(gè)序列中具有給定值的素有實(shí)例

#include<iostream>
#include<vector>
#include<algorithm>

using namespace std;

class IntCompare {
public:
    IntCompare(int v): val(v) {}
    bool operator ()(int v) { return val == v; }
private:
    int val;
};
int main()
{
    vector<int> vec = { 1,2,3,4,1 };
    const int oldValue = 1;
    const int newValue = 100;
    IntCompare icmp(oldValue);
    std::replace_if(vec.begin(), vec.end(), icmp, newValue);

    return 0;
}

利用函數(shù)對(duì)象作為replace_if算法的謂詞。
2、編寫(xiě)一個(gè)簡(jiǎn)單的桌面計(jì)算器使其能處理二元運(yùn)算

#include<iostream>
#include<map>
#include<algorithm>
#include<functional>
#include <string>
using namespace std;

map<string,function<int (int, int)>> binOps = {
    {"+", plus<int>()},
    {"-", minus<int>()},
    {"*", multiplies<int>()},
    {"/", divides<int>()},
    {"%", modulus<int>()}
};
int main()
{
    int a, b;
    string op;
    while (cin >> a >> op >> b) {
        cout << to_string(a) << op << to_string(b) << " = ";
        cout << binOps[op](a, b) << endl;
    }
    
    return 0;
}

運(yùn)行結(jié)果如下

image.png