UnionPattern.cs

using System.Collections.Generic;
using System.Threading.Tasks;
using Waher.Content.Semantic;
 
namespace Waher.Script.Persistence.SPARQL.Patterns
{
    public class UnionPattern : BinaryOperatorPattern
    {
        public UnionPattern(ISparqlPattern Left, ISparqlPattern Right)
            : base(Left, Right)
        {
        }
 
        public override async Task<IEnumerable<Possibility>> Search(ISemanticCube Cube, Variables Variables,
            IEnumerable<Possibility> ExistingMatches, SparqlQuery Query)
        {
            IEnumerable<Possibility> Matches1 = await this.Left.Search(Cube, Variables, ExistingMatches, Query);
            IEnumerable<Possibility> Matches2 = await this.Right.Search(Cube, Variables, ExistingMatches, Query);
 
            if (Matches1 is null)
                return Matches2;
            else if (Matches2 is null)
                return Matches1;
 
            if (!(Matches1 is LinkedList<Possibility> Result))
            {
                Result = new LinkedList<Possibility>();
 
                foreach (Possibility P in Matches1)
                    Result.AddLast(P);
            }
 
            foreach (Possibility P in Matches2)
                Result.AddLast(P);
 
            return Result;
        }
    }
}