Maybe lists are compared like strings?

So what do you recommend, Ali?

Agree with Ali

Yes, that's what happening. In C the strchr function returns a pointer to char, and in an expression every value of 0 evaluates to false (including the null pointer), and any non-null value to true. The ! operator evaluates to 1 if its argument is 0, and to 0 if it's argument is not equal to 0. We need twice the ! operator to turn any non-0 argument into 1.

ISO C17 6.5.3.3

I think the first "!" is to convert the pointer that strchr returns to a number(one if its a null pointer, and zero if the strchr found the specific character), so we can actually add to "int c". And the last "!", is to convert to the right number ,because null pointer was assigned to value one...

I assumed this based on sandoy's commentary... Might not be the right answer.

e.g. https://www.geeksforgeeks.org/designated-initializers-c/

If that's C then a string is a pointer so.. no?