Product.cs

using System.Collections.Generic;
using System.Numerics;
using Waher.Script.Abstraction.Elements;
using Waher.Script.Exceptions;
using Waher.Script.Model;
using Waher.Script.Objects;
using Waher.Script.Objects.VectorSpaces;
 
namespace Waher.Script.Functions.Vectors
{
    public class Product : FunctionOneVectorVariable
    {
        public Product(ScriptNode Argument, int Start, int Length, Expression Expression)
            : base(Argument, Start, Length, Expression)
        {
        }
 
        public override string FunctionName => nameof(Product);
 
        public override string[] Aliases
        {
            get { return new string[] { "prod", "∏" }; }
        }
 
        public override IElement EvaluateVector(DoubleVector Argument, Variables Variables)
        {
            return new DoubleNumber(CalcProduct(Argument.Values));
        }
 
        public static double CalcProduct(double[] Values)
        {
            double Result = 1;
            int i, c = Values.Length;
 
            for (i = 0; i < c; i++)
                Result *= Values[i];
 
            return Result;
        }
 
        public override IElement EvaluateVector(ComplexVector Argument, Variables Variables)
        {
            return new ComplexNumber(CalcProduct(Argument.Values));
        }
 
        public static Complex CalcProduct(Complex[] Values)
        {
            Complex Result = Complex.One;
            int i, c = Values.Length;
 
            for (i = 0; i < c; i++)
                Result *= Values[i];
 
            return Result;
        }
 
        public override IElement EvaluateVector(IVector Argument, Variables Variables)
        {
            return EvaluateProduct(Argument, this);
        }
 
        public static IElement EvaluateProduct(IVector Vector, ScriptNode Node)
        {
            return EvaluateProduct(Vector.VectorElements, Node);
        }
 
        public static IElement EvaluateProduct(ICollection<IElement> Elements, ScriptNode Node)
        {
            IRingElement Result = null;
            IRingElement RE;
            IRingElement Product;
 
            foreach (IElement E in Elements)
            {
                RE = E as IRingElement;
                if (RE is null)
                {
                    if (Elements.Count == 1)
                        return E;
                    else
                        throw new ScriptRuntimeException("Elements cannot be multiplied.", Node);
                }
 
                if (Result is null)
                    Result = RE;
                else
                {
                    Product = Result.MultiplyRight(RE);
                    if (Product is null)
                        Product = (IRingElement)Operators.Arithmetics.Multiply.EvaluateMultiplication(Result, RE, Node);
 
                    Result = Product;
                }
            }
 
            if (Result is null)
                return ObjectValue.Null;
            else
                return Result;
        }
 
    }
}