declare extract(string,_,_)

extract(tag, %s[@a x] y,q) when << s = tag >> -> %s[@a x] extract(tag,y,q)
extract(tag,_[_] y,q) -> extract(tag,y,q)
extract(_,(),q) -> q

split(person[@a name[str(n,_)] children[c] _] y,q) ->
  let tag = << match List.assoc "gender" a with "M"->"man" | _ ->"woman" >> in
  let c = split(c,()) in
  let sons = extract("man",c,()) in
  let daughters = extract("woman",c,()) in
  let a' = << ["name",n] >> in 
  %tag[ @a' sons[sons] daughters[daughters] ] split(y,q)

split(str(_,y),q) -> split(y,q)
split((),q) -> q

main(_[x] _) -> split(x,())