/// <summary>
/// Produces the set of active columns for the data view (as a bool[] of length bindings.ColumnCount),
/// a predicate for the needed active input columns, and a predicate for the needed active
/// output columns.
/// </summary>
public bool[] GetActive(Func <int, bool> predicate, out Func <int, bool> predicateInput)
{
var active = GetActive(predicate);
Contracts.Assert(active.Length == ColumnCount);
var activeInput = GetActiveInput(predicate);
Contracts.Assert(activeInput.Length == Input.ColumnCount);
// Get a predicate that determines which outputs are active.
var predicateOut = GetActiveOutputColumns(active);
// Now map those to active input columns.
var predicateIn = _mapper.GetDependencies(predicateOut);
// Combine the two sets of input columns.
predicateInput =
col => 0 <= col && col < activeInput.Length && (activeInput[col] || predicateIn(col));
return(active);
}