error: name lookup of 'i' changed for ISO 'for' scoping

问题

I have looked at other topics similar to this and still cannot find out what is wrong with my code. The following is a function in my program to find the Mean (Average) of Arrays. I get the error in the title: error: name lookup of 'i" changed for ISO 'for' scoping. following with note: if you use '-fpermissize' g++ will accept your code.

double GetMean ( double Array[], int ArrayLength )
{
    int Sum, Mean;
    for ( int i = 0; i < ArrayLength; i++ )
    {
         Sum = Sum + Array[i];
    }

    Mean = Sum / Array[i];

    return Mean;
}

Ideas and explanation would be lovely so I can understand what the hell I'm doing wrong :/

回答1:

for (int i = 0; i < ArrayLength; i++)

When you define i in the for header like this, its scope is inside the for loop. You can't use it outside the for loop like Mean = Sum / Array[i]; in your code.

Change it to:

int i;
for (i = 0; i < ArrayLength; i++)

Also note you never initialize Sum.

回答2:

This statement

Mean = Sum / Array[i];

makes no sense.

As for the error then you are trying to use varaible i in expression Array[i] in the statement above outside its scope. It is defined only within the loop.

Also you forgot to initialize variable Sum and I think it should have type double.

The function could look like

double GetMean( const double Array[], int ArrayLength )
{
    double  Sum = 0.0;

    for ( int i = 0; i < ArrayLength; i++ )
    {
         Sum = Sum + Array[i];
    }

    return ArrayLength == 0 ? 0.0 : Sum / ArrayLength;
}

来源：https://stackoverflow.com/questions/26552165/error-name-lookup-of-i-changed-for-iso-for-scoping

标签

c++

arrays

function

average

mean