Std.Ui.History

amend&Std.Ui.History.History[S] -> S -> Std.Ui.History.History[S]
The history with the present replaced and nothing recorded, for a change
fn
canRedo&Std.Ui.History.History[S] -> Bool
Whether a step forward exists.
fn
canUndo&Std.Ui.History.History[S] -> Bool
Whether a step back exists.
fn
depth&Std.Ui.History.History[S] -> (Int, Int)
How many steps back and forward exist.
fn
History
Undo and redo over whole states.
type
presentOf&Std.Ui.History.History[S] -> S
The current state.
fn
record&Std.Ui.History.History[S] -> S -> Std.Ui.History.History[S]
The history after a change to next: the present becomes undoable and
fn
redo&Std.Ui.History.History[S] -> Std.Ui.History.History[S]
The history one step forward, or unchanged when nothing can be redone.
fn
startS -> Int -> Std.Ui.History.History[S]
A history holding only present, keeping at most limit earlier states.
fn
undo&Std.Ui.History.History[S] -> Std.Ui.History.History[S]
The history one step back, or unchanged when nothing can be undone.
fn