static public ProcessWithLog <LogEntryT, Result <ErrT, NewOkT> > ResultAndThenMap <LogEntryT, ErrT, OkT, NewOkT>(
this ProcessWithLog <LogEntryT, Result <ErrT, OkT> > orig,
Func <OkT, Result <ErrT, NewOkT> > andThen) =>
orig.MapResult(previousResult =>
previousResult.Ok == null ?
new Result <ErrT, NewOkT>(Err: previousResult.Err) :
andThen(previousResult.Ok));
