Why doesn't a+++++b work?

Question

int main ()
{
   int a = 5,b = 2;
   printf(\"%d\",a+++++b);
   return 0;
}

This code gives the following error:

error: lval

Answer 1

Because it causes undefined behaviour.

Which one is it?

c = (a++)++ + b
c = (a) + ++(++b)
c = (a++) + (++b)

Yeah, neither you nor the compiler know it.

EDIT:

The real reason is the one as said by the others:

It gets interpreted as (a++)++ + b.

but post increment requires a lvalue (which is a variable with a name) but (a++) returns a rvalue which cannot be incremented thus leading to the error message you get.

Thx to the others to pointing this out.