Question

我试图将某个const值分配到特定条件。

例如，我有3个const值

const double highDiscount = 0.3;
const double midDiscount = 0.2;
const double lowDiscount = 0.1;

成本最高的产品应获得高折扣，而中间成本应获得midDiscount，最低成本应获得lowDiscount。

因此，我尝试使用if-else语句通过特定条件分配const。

double discount;

if (acost > bcost && acost > ccost)
{

    discount = highDiscount;

    if ( bcost < ccost)
    {
        discount = midDiscount;

    }
    else if ( ccost < bcost )
    {
        discount = lowDiscount;
    }
}

使用我的输出代码

cout << "acost has a" discount*100 << "% discount" << endl;
cout << "bcost has a" discount*100 << "% discount" << endl;
cout << "ccost has a" discount*100 << "% discount" << endl;

应产生以下结果

acost有30％的折扣

ccost有20％的折扣

bcost有10％的折扣

不幸的是，当我编译我的代码时，事实证明所有的a，b和c都有10％的折扣而不是分配的const值。

我错过了一些重要的重点吗？

Answer 1

在产品类中，添加＆lt;操作

bool operator< (const product &other) const {
    return cost < other.cost;
}

然后创建一个包含所有产品的向量。

vector<product> products;
products.push_back(product1);
products.push_back(product2);
products.push_back(product3);

对产品向量进行排序（按成本排序）

std::sort(products.begin(), products.end());

只需将折扣应用于已排序的元素

products[0].discount = lowDiscount;
products[1].discount = midDiscount;
products[2].discount = highDiscount;

这比嵌套的if语句更容易阅读和调试。

不完全确定您的代码有什么问题，如果没有看到完整的代码，很难说清楚。

编辑：由于您的代码逻辑存在根本性的错误，因此这里有一个完全包含的示例：

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


class product {
public:
    product(std::string name, double cost);
    ~product();
    //in product class, add the < operator
    bool product::operator< (const product &other) const;
    std::string Name;
    double Cost;
    double Discount;
};

product::product(std::string name, double cost) : Name(name), Cost(cost){}
product::~product(){}


const double highDiscount = 0.3;
const double midDiscount = 0.2;
const double lowDiscount = 0.1;

struct CompareProductPointers {
    bool operator()(const product* l, const product* r) {
        return *l < *r;
    }
};

int main() {
    //create a vector holding all your products
    product product1("product1", 10);
    product product2("product2", 8);
    product product3("product3", 12);

    std::vector<product*> products;
    products.push_back(&product1);
    products.push_back(&product2);
    products.push_back(&product3);

    //sort your product vector (which will sort by cost)
    std::sort(products.begin(), products.end(), CompareProductPointers());

    //apply your discount to the sorted elements
    products[0]->Discount = lowDiscount;
    products[1]->Discount = midDiscount;
    products[2]->Discount = highDiscount;

    //output
    std::cout << product1.Name << " has a " << (product1.Discount * 100) << "% discount" << std::endl;
    std::cout << product2.Name << " has a" << (product2.Discount * 100) << "% discount" << std::endl;
    std::cout << product3.Name << " has a" << (product3.Discount * 100) << "% discount" << std::endl;
    return 0;
}

使用嵌套的if else语句将const值分配到特定条件

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