Right.cs

using System;
using System.Collections.Generic;
using Waher.Script.Abstraction.Elements;
using Waher.Script.Abstraction.Sets;
using Waher.Script.Exceptions;
using Waher.Script.Model;
using Waher.Script.Objects;
 
namespace Waher.Script.Functions.Vectors
{
    public class Right : FunctionMultiVariate
    {
        public Right(ScriptNode X, ScriptNode N, int Start, int Length, Expression Expression)
            : base(new ScriptNode[] { X, N }, new ArgumentType[] { ArgumentType.Normal, ArgumentType.Scalar },
                  Start, Length, Expression)
        {
        }
 
        public override string FunctionName => nameof(Right);
 
        public override string[] DefaultArgumentNames
        {
            get { return new string[] { "x", "N" }; }
        }
 
        public override IElement Evaluate(IElement[] Arguments, Variables Variables)
        {
            double N = Expression.ToDouble(Arguments[1].AssociatedObjectValue);
            if (N < 0 || N > int.MaxValue || N != Math.Truncate(N))
                throw new ScriptRuntimeException("Expected nonnegative integer in second argument.", this);
 
            int c = (int)N;
 
            if (Arguments[0].AssociatedObjectValue is string s)
            {
                if (c > s.Length)
                    return Arguments[0];
                else
                    return new StringValue(s.Substring(s.Length - c, c));
            }
            else
            {
                ICollection<IElement> ChildElements;
 
                if (Arguments[0] is IVector Vector)
                {
                    if (Vector.Dimension <= c)
                        return Vector;
 
                    ChildElements = Vector.VectorElements;
                }
                else if (Arguments[0] is ISet Set)
                {
                    int? Size = Set.Size;
 
                    if (Size.HasValue && Size.Value <= c)
                        return Set;
 
                    ChildElements = Set.ChildElements;
                }
                else
                    throw new ScriptRuntimeException("First argument expected to be a string, vector or a set.", this);
 
                IElement[] Result = new IElement[c];
 
                if (ChildElements is IElement[] V)
                    Array.Copy(V, V.Length - c, Result, 0, c);
                else if (c > 0)
                {
                    int i = 0;
                    int j = c - ChildElements.Count;
 
                    foreach (IElement Element in ChildElements)
                    {
                        if (j++ >= 0)
                            Result[i++] = Element;
                    }
                }
 
                return Arguments[0].Encapsulate(Result, this);
            }
        }
 
    }
}