So there was a Reddit thread today that was diverging into bad coding tests plus grade evaluation puns (C++) – so I tried to make a purposefully confusing C program behave in a way that a coder or programmer wouldn’t exactly expect. After I wrote it, I had to put in some for-loop-printf-debug statements just to confirm and demonstrate how the right-to-left side value-lookup to delayed-increase to index-assignment works in C, it’s pretty neat to try and analyze how and why this is “working” lol!

#include <stdio.h>
int main()
{
    char A = 'A', B = 'B', C = 'C', D = 'D', E = 'E', F = 'F';
    char grades[256];
    grades[A++] = A++;
    grades[B++] = B++;
    grades[C++] = C++;
    grades[D++] = D++;
    grades[E++] = E++;
    grades[F++] = F++;
    printf("My grade is %c!\n",grades[C++]);
}

And basically this will print out “My grade is D!” – but it’s fun to trace through how each line will process the value statement first and then the assignment index is processed afterwards. In addition, each line will affect the next statement below because of the increases that take place in between processing sides, so the future lookup index values are being changed along the way! 🙂