/* input e.g. [[

prelude

title

-----

text

title 2

-------

text

]] */

static SS underlinedHeadingSections(S text) {

  LS lines = lines(text);

  L<Int> l = indicesOfStartingWithTrim(lines, "--");

  new LinkedHashMap<S> out;

  if (nempty(l))

    mapPutIfNemptyValue(out, "", rtrim(lines(takeFirst(lines, first(l)-1))));

  for i over l: {

    int i1 = get(l, i);

    int i2 = or(get(l, i+1), l(lines)+1);

    S heading = trim(get(lines, i1-1));

    out.put(heading, lines(subList(lines, i1+1, i2-1)));

  }

  ret out;

}