FindElements.cs

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;
using Waher.Script.Objects.Matrices;
using Waher.Script.Objects.VectorSpaces;
 
namespace Waher.Script.Functions.Matrices
{
    public class FindElements : FunctionMultiVariate
    {
        public FindElements(ScriptNode SearchFor, ScriptNode In, int Start, int Length, Expression Expression)
            : base(new ScriptNode[] { SearchFor, In }, new ArgumentType[] { ArgumentType.Scalar, ArgumentType.Normal },
                  Start, Length, Expression)
        {
        }
 
        public override string FunctionName => nameof(FindElements);
 
        public override string[] DefaultArgumentNames => new string[] { "SearchFor", "In" };
 
        public override IElement Evaluate(IElement[] Arguments, Variables Variables)
        {
            IElement SearchFor = Arguments[0];
            IElement In = Arguments[1];
 
            if (In is IMatrix M)
            {
                List<IElement> Coordinates = new List<IElement>();
                int Rows = M.Rows;
                int Columns = M.Columns;
                int x, y;
 
                for (y = 0; y < Rows; y++)
                {
                    for (x = 0; x < Columns; x++)
                    {
                        if (SearchFor.Equals(M.GetElement(x, y)))
                        {
                            Coordinates.Add(new DoubleNumber(x));
                            Coordinates.Add(new DoubleNumber(y));
                        }
                    }
                }
 
                return new DoubleMatrix(Coordinates.Count / 2, 2, Coordinates);
            }
            else if (In is IVector V)
            {
                List<double> Indices = new List<double>();
                int i = 0;
 
                foreach (IElement Element in V.VectorElements)
                {
                    if (SearchFor.Equals(Element))
                        Indices.Add(i);
 
                    i++;
                }
 
                return new DoubleVector(Indices.ToArray());
            }
            else if (In is ISet S)
            {
                List<double> Indices = new List<double>();
                int i = 0;
 
                foreach (IElement Element in S.ChildElements)
                {
                    if (SearchFor.Equals(Element))
                        Indices.Add(i);
 
                    i++;
                }
 
                return new DoubleVector(Indices.ToArray());
            }
            else
                throw new ScriptRuntimeException("Expected second argument to be matrix, vector or set.", this);
        }
    }
}