bool replace = false;
for (int pars = 0, bracks = 1; bracks > 0 and pos < len; ++pos) {
  if (synt[pos] == '(') {
    ++pars;
  } else if (synt[pos] == ')') {
    --pars;
  } else if (synt[pos] == '[') {
    ++bracks;
  } else if (synt[pos] == ']') {
    --bracks;
  } else if (synt[pos] == ',' and pars == 0 and bracks == 1) {
    replace = true;
    break;
  }
}