这个C++代码有什么问题？(安慰)

Question

对我来说,这段代码似乎没有错误,而且我学习C++的方式也是正确的.可能有什么不对？

这是我的代码:

#include<iostream>
#include<cstdlib>
#include<string>
#include<cmath>
using namespace std;

double Calculation(long double x, long double y);
void Output(long double s, long double d, long double p, long double q);

void main(){

    long double a;
    long double b;
    long double sum;
    long double difference;
    long double product;
    long double quotient;
    cout << "Enter your first number." << endl;
    cin >> a;
    cout << "Enter your second number." << endl;
    cin >> b;

    Calculation(a, b);
    Output(sum, difference, product, quotient);


    system("pause");
}


double Calculation(long double x, long double y){
    long double sum;
    long double difference;
    long double product;
    long double quotient;
    sum = x + y;
    difference = x - y;
    product = x * y;
    quotient = x / y;
    return sum;
    return difference;
    return product;
    return quotient;
}

void Output(long double s, long double d, long double p, long double q){

    cout << "The sum of your numbers is " << s << "." << endl;
    cout << "The difference between your numbers is " << d << "." << endl;
    cout << "The product of your numbers is " << p << "." << endl;
    cout << "The quotient of your numbers is " << q << "." << endl;



}

说明:这是一个按变量'a'和'b'工作的计算器.它通过函数Calculate计算'a'和'b'的和,差,乘积和商,并用函数Output输出答案.

Error: uninitialized local variable 'quotient' used.
uninitialized local variable 'product' used.
uninitialized local variable 'difference' used.
uninitialized local variable 'sum' used.

Answer 1

您的代码有很多问题,但是有一个根本原因 - 对return语句如何工作的误解.

你有一个多return语句的功能.您似乎认为所有这些陈述都会执行; 那个假设是不正确的.只return执行函数中的第一个语句; 其余的被忽略了.

而且,您似乎暗示该return语句会自动影响调用者中的变量; 它不会.为了修改调用者中的变量,调用者本身需要分配返回的值.

如果您需要函数返回多个值,则需要更改方法:它应该通过引用获取多个参数,并修改它们,如下所示:

void Calculation(long double x, long double y, long double &sum,
    long double &difference, long double &product, long double &quotient) {
    sum = x + y;
    difference = x - y;
    product = x * y;
    quotient = x / y;
}

您还需要更改原型声明Calculation,如下所示:

void Calculation(long double x, long double y, long double &sum,
    long double &difference, long double &product, long double &quotient);

Calculation像这样打电话:

Calculation(a, b, sum, difference, product, quotient);

这将解决您的编译问题,代码将正确运行.