C语言 二进制表达式的无效操作数，C
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Invalid Operands to binary Expression, C
提问by aprohl5
Im working on a function that takes some values and finds the min, max, and average of the values. I'm passing everything to the function by reference and am getting some errors when I try and do basic operations like +and /Namely the error is
我正在研究一个函数，它接受一些值并找到这些值的最小值、最大值和平均值。我通过引用将所有内容传递给函数，并且在尝试执行基本操作时遇到一些错误，例如+，/即错误是
Invalid operands to binary expression ('double *' and 'double *')
二进制表达式的无效操作数（'double *' 和 'double *'）
void MinMaxAvg(double *pA, double *min, double *max, double *avg, int lines, double *total )
{
for (int i=0; i<lines; i++)
{
if ( i==0)
{
min = &pA[0];
max = &pA[0];
}
else
{
if (&pA[i] < min)
{
min = &pA[i];
}
if (&pA[i] > max)
{
max = &pA[i];
}
}
total += &pA[i]; //<-- Errors on this line
}
avg = (total / lines); // <-- Errors on this line.
}
回答by Magnus
It seems like you're getting some of the types confused there. In your example you're setting the pointersto a new value, not the value of said pointers.
似乎您在那里混淆了某些类型。在您的示例中，您将指针设置为新值，而不是所述指针的值。
The first would have to be:
第一个必须是：
*total += pA[i];
While the second should be:
而第二个应该是：
*avg = (*total / lines);
In fact, you probably want to use floating point division on the second error there (some compilers are notorious for using integer divison in unexpected places):
事实上，您可能想在第二个错误上使用浮点除法（一些编译器因在意想不到的地方使用整数除法而臭名昭著）：
*avg = (*total / (double)lines);
You'll still be getting errors if you do it like that, however. For example &pA[i] > ...will result in a pointer comparison, i.e. the addressof the pointers will be compared. Most likely not what you want.
但是，如果您这样做，您仍然会遇到错误。例如&pA[i] > ...将导致指针比较，即将比较指针的地址。很可能不是你想要的。
回答by unwind
You're trying to add an address to a pointer, that's not a valid operation.
您正在尝试向指针添加地址，这不是有效的操作。
You probably meant:
你可能的意思是：
*total += pA[i];
Your use of &pAseems very confused, as does the re-assignment of the pointers minand max.
您的使用&pA似乎很混乱，指针min和的重新分配也是如此max。
If you have a pointer to a value (like double *min), then *minis how you access (read or write) the value being pointed at.
如果您有一个指向值的指针（如double *min），那么*min就是您访问（读取或写入）所指向的值的方式。
回答by oleg_g
There is no "pass by reference" in C language unlike C++. You should dereference each pointer in your code if you want work with variables values. Now you work with variables addresses.
与 C++ 不同，C 语言中没有“通过引用传递”。如果您想使用变量值，您应该取消引用代码中的每个指针。现在您使用变量地址。
