c++ - lvalue required as increment operand error

Question

#include <stdio.h>

int main()
{
   int i = 10;
   printf("%d
", ++(-i)); // <-- Error Here
}

What is wrong with ++(-i)? Please clarify.

Answer 1

-i generates a temporary and you can't apply ++ on a temporary(generated as a result of an rvalue expression). Pre increment ++ requires its operand to be an lvalue, -i isn't an lvalue so you get the error.