MultiplyElementWise.cs

using System;
using Waher.Script.Abstraction.Elements;
using Waher.Script.Exceptions;
using Waher.Script.Model;
using Waher.Script.Objects;
 
namespace Waher.Script.Operators.Arithmetics
{
    public class MultiplyElementWise : BinaryElementWiseOperator, IDifferentiable
    {
        public MultiplyElementWise(ScriptNode Left, ScriptNode Right, int Start, int Length, Expression Expression)
            : base(Left, Right, Start, Length, Expression)
        {
        }
 
        public override IElement EvaluateScalar(IElement Left, IElement Right, Variables Variables)
        {
            if (Left.AssociatedObjectValue is double DL && Right.AssociatedObjectValue is double DR)
                return new DoubleNumber(DL * DR);
            else
                return Multiply.EvaluateMultiplication(Left, Right, this);
        }
 
        public ScriptNode Differentiate(string VariableName, Variables Variables)
        {
            if (this.left is IDifferentiable Left &&
                this.right is IDifferentiable Right)
            {
                int Start = this.Start;
                int Len = this.Length;
                Expression Expression = this.Expression;
 
                return new Add(
                    new MultiplyElementWise(
                        Left.Differentiate(VariableName, Variables),
                        this.right,
                        Start, Len, Expression),
                    new MultiplyElementWise(
                        this.left,
                        Right.Differentiate(VariableName, Variables),
                        Start, Len, Expression),
                    Start, Len, Expression);
            }
            else
                throw new ScriptRuntimeException("Factors not differentiable.", this);
        }
 
    }
}