datatype lines = End | Line of source lines
type t = { Head : source lines, Tail : source (source lines) }
val create =
head <- source End;
tail <- source head;
return {Head = head, Tail = tail}
fun renderL lines =
case lines of
End =>
| Line linesS => X
and renderS linesS =
lines <- signal linesS;
return (renderL lines)
fun render t = renderS t.Head
fun write t =
oldTail <- get t.Tail;
newTail <- source End;
set oldTail (Line newTail);
set t.Tail newTail
fun main () : transaction page =
b <- create;
return