Check the Correct Balance of Brackets in Arithmetic Expressions

The following function returns 0 if the brackets in the expression are well balanced, and a nonzero integer if not.

int balanced(char *str)
{
   int balance=0;  // Balance indicator.
   char c;  // Current character.
   int i=0;  // Character index.
   // Read characters.
   while((c=str[i++]) != '\0')
   {
      // When '(' is read, increase indicator.
      if(c=='(') balance++;
      // When ')' is read, decrease indicator.
      if(c==')') balance--;
   }
   return balance;
}