FirstEvaluator.cs

using Waher.Script.Abstraction.Elements;
using Waher.Script.Model;
using Waher.Script.Objects;
 
namespace Waher.Script.Functions.Vectors
{
    public class FirstEvaluator : UnaryIterativeEvaluator
    {
        private IElement first = null;
 
        public FirstEvaluator(First Node)
            : base(Node.Argument)
        {
        }
 
        public override void RestartEvaluator()
        {
            this.first = null;
        }
 
        public override void AggregateElement(IElement Element)
        {
            if (this.first is null)
                this.first = Element;
        }
 
        public override IElement GetAggregatedResult()
        {
            return this.first ?? ObjectValue.Null;
        }
    }
}