Required.cs

using System.Collections.Generic;
using System.Threading.Tasks;
using Waher.Script.Abstraction.Elements;
using Waher.Script.Exceptions;
using Waher.Script.Model;
 
namespace Waher.Script.Functions.Runtime
{
    public class Required : FunctionOneVariable
    {
        public Required(ScriptNode Argument, int Start, int Length, Expression Expression)
            : base(Argument, Start, Length, Expression)
        {
        }
 
        public override string FunctionName => nameof(Required);
 
        public override IElement Evaluate(Variables Variables)
        {
            IElement E = this.Argument.Evaluate(Variables);
            if (E.AssociatedObjectValue is null)
                throw new ScriptRuntimeException("Not defined.", this);
 
            return E;
        }
 
        public override async Task<IElement> EvaluateAsync(Variables Variables)
        {
            IElement E = await this.Argument.EvaluateAsync(Variables);
            if (E.AssociatedObjectValue is null)
                throw new ScriptRuntimeException("Not defined.", this);
 
            return E;
        }
 
        public override IElement Evaluate(IElement Argument, Variables Variables)
        {
            return Argument;
        }
 
        public override PatternMatchResult PatternMatch(IElement CheckAgainst, Dictionary<string, IElement> AlreadyFound)
        {
            if (CheckAgainst.AssociatedObjectValue is null)
                return PatternMatchResult.NoMatch;
 
            return this.Argument.PatternMatch(CheckAgainst, AlreadyFound);
        }
    }
}