class virtual make :id:string -> title:string -> descr:string -> params:parameter list ->object..end
method id : string
method reset : unit
method get_field : 'a. 'a field -> 'a
method set_field : 'a. 'a field -> 'a -> unit
method title : string
method descr : string
method params : parameter list
method reset : unitReset all parameters to default
method virtual select : feedback -> selection -> statusShall return Applicable or Not_configured
if the tactic might apply to the selection.
Hints can be provided here, if appropriate.
The continuation f returned with Applicable f shall generates
sub-goals wrt to the given selection and current field values.
Exit,Not_found is like returning Not_applicable.