Question

我们应该创建一个“结构”，允许用户输入两个向量（x1，y1）和（x2，y2）并创建添加和减去向量的函数。我以为我的代码结构是正确的，但我在加法和减法函数中遇到错误，我不知道为什么。总决赛正在摧毁我。请指出我正确的方向。

/*
v1=(a,b)   v2=(c,d)
v1+v2 = (a,b)+(c,d) = (a+c, b+d)
v1-v2 = (a,b)-(c,d) = (a-c, b-d)

define an array of two mathematical vector structures
each structure consists of two double-precision components, a and b
permit user to enter two vectors, call two functions to return the sum and 
difference
display results calculated

*/

#include <iostream>
using namespace std;

struct Vector
{
    double X;
     double Y;
} v1, v2;


//prototypes for add and subtract functions
double addVector(Vector vectadd);
double subtVector(Vector vectsub);

int main()
{
    cout << "This program will add and subtract two vectors." << endl;
    cout << "Enter X1: " << endl;
    cin >> v1.X;
    cout << "Enter Y1: " << endl;
    cin >> v1.Y;
    cout << "Enter X2: " << endl;
    cin >> v2.X;
    cout << "Enter Y2: " << endl;
    cin >> v2.Y;

    addVector(v1);
    subtVector(v2);

    return 0;
}

double addVector(Vector vectadd)
{
    cout << "When added together, (x1, y1) + (x2, y2) becomes: " << endl;
    cout << "(" << (v1.X + v2.X) << "," << (v1.Y + v2.Y) << ")" << endl;
}

double subtVector(Vector vectsub)
{
    cout << "When subtracted from one another, (x1, y1) - (x2, y2) becomes: " << 
endl;
    cout << "(" << (v1.X - v2.X) << "," << (v1.Y - v2.Y) << ")" << endl;
}

编辑：我将函数更改为VOID函数，现在代码按预期工作。这可能不是完成这项任务的最优雅方式，对吗？

#include <iostream>
using namespace std;

struct Vector
{
double X;
double Y;
}v1, v2;


//prototypes for add and subtract functions
void addVector (Vector vectadd);
void subtVector (Vector vectsub);

int main()
{


cout << "This program will add and subtract two vectors." << endl;
cout << "Enter X1: ";
cin >> v1.X;
cout << "\nEnter Y1: ";
cin >> v1.Y;
cout << "\nEnter X2: ";
cin >> v2.X;
cout << "\nEnter Y2: ";
cin >> v2.Y;
cout << endl;

addVector (v1);
subtVector (v2);


return 0;
}

void addVector (Vector vectadd)
{
cout << "When added together, (x1, y1) + (x2, y2) becomes: " << endl;
cout << "(" << (v1.X + v2.X) << "," << (v1.Y + v2.Y) << ")" << endl;
}

void subtVector (Vector vectsub)
{
cout << "When subtracted from one another, (x1, y1) - (x2, y2) becomes: " << endl;
cout << "(" << (v1.X - v2.X) << "," << (v1.Y - v2.Y) << ")" << endl;

Answer 1

您的代码未编译，原因在于消息：

'subtVector'：必须返回一个值

提示，该函数也应该返回一个向量， addVector函数可能如下所示：

Vector addVector(Vector& vA, Vector& vB)
{
    Vector r;
    r.X = vA.X + vB.X;
    r.Y = vA.Y + vB.Y;

    cout << "When added together, (x1, y1) + (x2, y2) becomes: " << endl;
    cout << "(" << r.X << "," << r.Y << ")" << endl;
    return r; 
}

同样适用于 subVector

Answer 2

函数void或具有其他数据类型。

请注意：

void f()
{
    // this function does something, but it does NOT have to return anything because 
    //it is a void function 
}

但

int fun()
{
  // does something
  return expression;
}

此函数必须返回一个值，因为它不是void函数。在这种情况下，它必须返回int值。

void类型的函数可以直接调用

//code
f();
// code

但non-void函数可以分配给其他变量，如：

// code
v = fun();

或者可以是

这样的表达式的一部分

//code
cout << 5 + fun();

因此...

让你的功能像这样无效

void addVector(Vector vectadd);
void subtVector(Vector vectsub);


void addVector(Vector vectadd)
{
   // your code
}

void subtVector(Vector vectsub)
{
   // your code
}

或者，您可以从函数返回向量而不是double。

Vector addVector (Vector , Vector);
Vector subtVector (Vector , Vector);

int main()
{
    // your code
    Vector V;

    cout << "When added together, (x1, y1) + (x2, y2) becomes: " << endl;
     V = addVector (v1, v2);
    cout << "(" << V.X << "," << V.Y << ")" << endl;

     V = subtVector (v1, v2);
    cout << "When added together, (x1, y1) + (x2, y2) becomes: " << endl;
    cout << "(" << V.X << "," << V.Y << ")" << endl;

    return 0;
}

Vector addVector (Vector v1, Vector V2)
{
    Vector Result;
    Result.X = v1.X + v2.X;
    Result.Y = v1.Y + v2.Y; 
    return  Result;
}


Vector subtVector (Vector v1, Vector V2)
{
    Vector Result;
    Result.X = v1.X - v2.X;
    Result.Y = v1.Y - v2.Y;   
    return  Result;
}

使用结构添加和减去矢量

2 个答案: