typedef struct { char *b, *e; } range;
typedef struct { range a, b; } two_ranges;

two_ranges find_cset(range s, range delims)
{
  char *b = s.b;
  for (; s.b != s.e; s.b++) {
    for (char *t = delims.b; t != delims.e; t++) {
      if (*t == *s.b) return (two_ranges) { { b, s.b }, s };
    }
  }
  return (two_ranges) { { b, s.b }, s };
}