得到两个不同的答案 [英] Getting two different answers

问题描述

我很好奇当我将公式传递给变量'gcon'时我没有得到正确答案，为什么会这样？数据类型是否影响答案以及如何影响？



我尝试过：

I'm curious when I pass the formula into the variable 'gcon' I don't get the correct answer, why is that? Does the data type affect's the answer and how?

What I have tried:

#include <iostream>
using namespace std;

int main()
{

    double ml;
    double gcon = ml*0.00026417; // milliliters to gallons conversion
    cout << "type the amount of milliliters\n";
    cin >> ml;
    cout << "milliliters to gallons is  " << ml*0.00026417 << endl;
    cout << "milliliters to gallons is " << gcon << endl;
    
    return 0;
}

推荐答案

如果仔细观察，在将值放入之前，您将看到使用变量ml它。到那时为止，这个变量的值是在为它分配的内存中发生的事情。

If you look carefully, you will see that you are using the variable ml before you put a value into it. Up to then the value of this variable is that what happens to be in the memory allocated for it.

有一个工具可以让你看到你的代码在做什么，它的名字是调试器。掌握调试器不是可选的，它对任何程序员都是强制性的，也不例外。

它也是一个很好的学习工具，因为它向你展示了现实，你可以看到哪个期望与现实相符。

当你不明白你的代码在做什么或为什么它做它的作用时，答案是调试器。

使用调试器查看你的代码是什么代码正在做。只需设置断点并查看代码执行情况，调试器允许您逐行执行第1行并在执行时检查变量，这是一个令人难以置信的学习工具。



调试器 - 维基百科，免费的百科全书 [ ^ ]

掌握Visual Studio 2010中的调试 - 初学者指南 [ ^ ]

使用Visual Studio 2010进行基本调试 - YouTube [ ^ ]

调试器在这里向您展示您的代码正在做什么以及您的任务是与它应该做的比较。

调试器中没有魔法，它没有发现错误，它只是帮助你。当代码没有达到预期的效果时，你就会接近一个错误。

There is a tool that allow you to see what your code is doing, its name is debugger. Mastering the debugger is not optional, it is mandatory for any programmer, no exception.
It is also a great learning tool because it show you reality and you can see which expectation match reality.
When you don't understand what your code is doing or why it does what it does, the answer is debugger.
Use the debugger to see what your code is doing. Just set a breakpoint and see your code performing, the debugger allow you to execute lines 1 by 1 and to inspect variables as it execute, it is an incredible learning tool.

Debugger - Wikipedia, the free encyclopedia[^]
Mastering Debugging in Visual Studio 2010 - A Beginner's Guide[^]
Basic Debugging with Visual Studio 2010 - YouTube[^]
The debugger is here to show you what your code is doing and your task is to compare with what it should do.
There is no magic in the debugger, it don't find bugs, it just help you to. When the code don't do what is expected, you are close to a bug.

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