static abstract class o_KnowingSolver {
  abstract void solve(L<Para> examples, Para target);
}

static void optimizeLastLine(L<Para> paras, O solver) {
  int score = 0;
  for (Para p : paras) {
    S method = optimizeLastLine(paras, p);
    if (notNull(method)) {
      print(p.index + " = " + method);
      ++score;
    }
  }
      
  print("Successfully calculated last lines: " + score + " of " + l(paras));
}

// returns calculation method if pivot could be calculated from other paragraphs
static S optimizeLastLine(L<Para> all, Para pivot) {
  L<Para> rest = listMinus(all, pivot);
  Para shortened = new Para(pivot.index, dropLastLine(pivot.text));
  ret optimizeLastLine_solve(rest, shortened);
}

optimizeLastLine_solve(L<Para> examples, Para target) {
  S lastLine = lastLine(pivot.text);
}