c++ - 未初始化的局部变量

Question

我是新手，刚开始学习 C++，遇到了这个问题，我可能花了一个小时试图修复和研究答案，但我似乎无法弄清楚我做错了什么。我使用 Visual Studios 作为我的 IDE，这是最新版本。

#include "stdafx.h"
#include <iostream>
#include "constant.h"

//height of the tower
double towerHeight(double x)
{
    using namespace std;
        cout << "Enter a height for the tower" << '\n';
        cin >> x;

        return x;
}

//the number of seconds since the ball has been dropped to determine the distance
double secondsSinceDrop(double x)
{
    using namespace std;
        cout << "How long has it been since you dropped the ball (Seconds): ";
        cin >> x;

        return x;
}

//finds how far off the ground the ball is 
double currentBallHeight(double x, double y)
{
    return y * constant::gravity - x;
}

//prints how far off the ground the ball is
void printResult(double x, double y)
{
    using namespace std;
        if (currentBallHeight(x, y) < 0)
            cout << "At " << y << " the ball is on the ground." << '\n';
        else
            cout << "At " << y << " the ball is at: " << currentBallHeight(x, y) << '\n';
}

int main()
{
    double x = towerHeight(x);
    double y = secondsSinceDrop(x);

    printResult(x,y);

    return 0;
}

这是错误代码- 第 2 章综合测验(第 2 部分).cpp(46):错误 C4700:使用了未初始化的局部变量“x”

-第(46)行是-double x = towerHeight(x);

我一直遇到这个问题，我已经更改了我的代码以将其归结为这个错误，但我不知道如何修复它。它可能很简单，我很愚蠢地忽略了它，但我们将不胜感激任何帮助。

Answer 1

These lines will be throwing errors
because the variable 'x' you are sending as an argument does not exist in the scope of main

 int main()
 {
 ->  double x = towerHeight(x);
 ->  double y = secondsSinceDrop(x);

     printResult(x,y);

     return 0;
 }

相反，您可以尝试这样的事情。

#include "stdafx.h"
#include <iostream>
#include "constant.h"
using namespace std;

//height of the tower
double towerHeight()
{
    double height;
    cout << "Enter a height for the tower" << '\n';
    cin >> height
    return height;
}

//the number of seconds since the ball has been dropped to determine the distance
double secondsSinceDrop()
{
    double seconds;
    cout << "How long has it been since you dropped the ball (Seconds): ";
    cin >> seconds;
    return seconds;
}

//finds how far off the ground the ball is 
double currentBallHeight(double x, double y)
{
    return y * constant::gravity - x;
}

//prints how far off the ground the ball is
void printResult(double x, double y)
{
    if (currentBallHeight(x, y) < 0)
        cout << "At " << y << " the ball is on the ground." << '\n';
    else
        cout << "At " << y << " the ball is at: " << currentBallHeight(x, y) << '\n';
}

int main()
{
    double height = towerHeight();
    double seconds = secondsSinceDrop();

    printResult(height, seconds);

    return 0;
}

一些我会推荐的技巧

• Declare your variables as much as relevant to you instead of using 'x/y/z'
• There is no need to add the using namespace std; inside each function