private static Maybe <QueryPlan> Op(Maybe <QueryPlan> left, Maybe <QueryPlan> right, Operation operation)
{
if (left.HasValue && right.HasValue)
{
switch (operation)
{
case Operation.And:
return(Maybe.Return(QueryPlan.And(left.Value, right.Value)));
case Operation.Or:
return(Maybe.Return(QueryPlan.Or(left.Value, right.Value)));
default:
throw new ArgumentException("{0} is not supported.".Fmt(operation));
}
}
return(left.HasValue ? left : right);
}