为什么这个关于指针的代码不起作用？ [英] why dosen't this code about pointers work ?

问题描述

#include<iostream>

using namespace std;

int main()
{
    double *iii=123;
    cout << *(iii);

    cin.get();

    return 0;

}

这是一个使用指针的简单代码，为什么不呢？ ork

为什么给编译器打电话说无效转换从int到int *

this is a simple code using pointers, why dosen't it work
why dose the compiler thwor an aeeor saying "invalid conversion from int to int*"

推荐答案

嗯...让我们看看就这样。

Well... lets look at it this way.

double *iii

声明一个名为iii的变量，它是一个指向double的指针。这意味着它包含双值的地址，因此名称为指针 - 它指向值。

declares a variable called "iii" which is a pointer to a double. Which means that it contains the address of double values, hence the name "pointer" - it "Points" to the value.

123

是一个可被视为双倍的数字。

所以

Is a number which can be treated as a double.
So

double *iii=123

声明指向double的指针并尝试将double值放入其中。不是双倍的地址，而是价值本身。



如果你认为汽车钥匙是汽车的指针那么你就是在试驾钥匙而不是车！



我想你需要回到你的讲义并再次阅读这些内容，但如果第一行可以工作，你这样做了：

Declare a pointer to a double and tries to put a double value into it. Not the address of a double, but the value itself.

If you think of a car key as the "pointer" to a car then you are trying to drive the key instead of the car!

I think you need to go back to your lecture notes and read through this stuff again, but the first line could be made to work if you did this:

double vd = 123;
double *iii=&vd;

因为在这种情况下，您将双精度数的地址放入指针中。请注意，您无法获取常量的地址：

Because in this case you are putting the address of a double into the pointer. Note that you can't take the address of a constant:

double *iii=&123;

因为那时你可以尝试修改常量而且PC Pixies不喜欢你试图这样做...

because then you could try to modify constants and the PC Pixies don't like you trying to do that...

Quote：

double * iii = 123;

double *iii=123;

上面的行是错的（指针必须指向。你需要类似的东西：

The above line is wrong (a pointer must point. You need something like:

double d = 123.0;
double *iii; // pointer variable declaration
iii = &d; // pointer variable initialisation

您可以将最后两行简写为：

You may short-cut the last two lines into:

double *iii = &d; // pointer variable declaration and initialisation

你需要将声明和初始化分开，例如：

You need to separate the declaration and initialization, like;

double *iii;
*iii = 123;

在原始代码中，您尝试设置指针 iii 到值 123 。由于 iii 是指针，因此需要将其设置为值的地址，而不是值本身。并且你不能用直接常量来做这个，所以你需要像上面那样拆分表达式。​​

In your original code you are trying to set the pointer iii to the value 123. And since iii is a pointer it needs to be set to the address of a value, rather than the value itself. And you cannot do this with a direct constant so you need to split the expression as above.

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