我的c函数在做什么错

Question

int SumBetween(int low, int high)
{
    int i;
    int end;
    int Ray[high - low];
    int sum;

    end = (high - low);

    for (i = 1; i = end; i++) {
        Ray[i] = low + i;
    }

    sum = 0;
    for (i = 1; i = end; i++) {
        sum = sum + Ray[i];
    }

    return sum;
}

The function above keep coming with this error:

main.c: In function 'SumBetween':
main.c:12:2: error: suggest parentheses around assignment used as truth value [-Werror=parentheses]
for (i = 1; i = end; i++) {
^
main.c:17:2: error: suggest parentheses around assignment used as truth value [-Werror=parentheses]
for (i = 1; i = end; i++) {
^
cc1: all warnings being treated as errors

what am I doing wrong?

Answer 1

Your problem is not technically error, but a warning. In your case, all warnings are represented as errors, because compiler detected possible problem in your code.

As seen, you have a problem in your for loop:

1. First is meant as assignment, usually i = 0 as arrays starts with 0 in C
2. This is condition, any assignment in condition should be in parenthesis
3. Third is increment or anything else (new assignment)

According to your code, you should rewrite your for loops to

//Start with i = 0 and go till end variable
//   1      2        3
for (i = 0; i < end; i++) {
    Ray[i] = low + i;
}

Answer 2

Technically you're for() statement is a endless loop, if end! = 0 end! = 0 . Assuming that high is greater than low (or values is equal), you can avoid the second loop by doing as follows:

int SumBetween(int low, int high)
{
    int i, end, sum = 0;

    end = (high - low);

    for (i = 1; i != end; i++) {
        sum += low + i;
    }

    return sum;
}

Btw, my proposal relies on the assumptions that you are need to reach end value from i = 1