{ $class-description "History models record a timeline of previous values on calls to " { $link add-history } ", and can travel back and forth on the timeline with " { $link go-back } " and " { $link go-forward } ". History models are constructed by " { $link <history> } "." } ;
HELP:<history>
{ $values { "value"object } { "history""a new " { $link history } } }
{ $description "Creates a new history model with an initial value." } ;
{ $description "Restores the previous value and calls " { $link model-changed } " on all observers registered with " { $link add-connection } "." } ;
HELP:go-forward
{ $values { "history" history } }
{ $description "Restores the value set prior to the last call to " { $link go-back } " and calls " { $link model-changed } " on all observers registered with " { $link add-connection } "." } ;
HELP:add-history
{ $values { "history" history } }
{ $description "Adds the current value to the history." } ;