LastIndexOf.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 LastIndexOf : FunctionMultiVariate
    {
        public LastIndexOf(ScriptNode Vector, ScriptNode Item, int Start, int Length, Expression Expression)
            : base(new ScriptNode[] { Vector, Item }, new ArgumentType[] { ArgumentType.Normal, ArgumentType.Scalar },
                  Start, Length, Expression)
        {
        }
 
        public LastIndexOf(ScriptNode Vector, ScriptNode Item, ScriptNode From, int Start, int Length, Expression Expression)
            : base(new ScriptNode[] { Vector, Item, From }, new ArgumentType[] { ArgumentType.Normal, ArgumentType.Scalar, ArgumentType.Scalar },
                  Start, Length, Expression)
        {
        }
 
        public override string FunctionName => nameof(LastIndexOf);
 
        public override string[] DefaultArgumentNames
        {
            get { return new string[] { "Vector", "Item" }; }
        }
 
        public override IElement Evaluate(IElement[] Arguments, Variables Variables)
        {
            IElement Vector = Arguments[0];
            IElement Item = Arguments[1];
            IElement From = Arguments.Length > 2 ? Arguments[2] : null;
            int FromIndex;
 
            if (From is null)
                FromIndex = int.MaxValue;
            else
                FromIndex = (int)Expression.ToDouble(From.AssociatedObjectValue);
 
            if (Vector.AssociatedObjectValue is string s1 && Item.AssociatedObjectValue is string s2)
            {
                if (From is null)
                    return new DoubleNumber(s1.LastIndexOf(s2));
 
                return new DoubleNumber(s1.LastIndexOf(s2, FromIndex));
            }
            else
            {
                ICollection<IElement> ChildElements;
 
                if (Vector is IVector V)
                    ChildElements = V.VectorElements;
                else if (Vector is ISet S)
                    ChildElements = S.ChildElements;
                else
                    throw new ScriptRuntimeException("Expected string arguments, or the first argument to be a vector or a set.", this);
 
                if (ChildElements is IElement[] V2)
                    return new DoubleNumber(Array.LastIndexOf(V2, Item));
 
                int i = 0;
                int Result = -1;
 
                foreach (IElement Element in ChildElements)
                {
                    if (Item.Equals(Element))
                        Result = i;
 
                    if (++i > FromIndex)
                        break;
                }
 
                return new DoubleNumber(Result);
            }
        }
 
    }
}