PowerElementWise.cs

using System;
using Waher.Script.Abstraction.Elements;
using Waher.Script.Exceptions;
using Waher.Script.Functions.Analytic;
using Waher.Script.Model;
using Waher.Script.Objects;
 
namespace Waher.Script.Operators.Arithmetics
{
    public class PowerElementWise : BinaryElementWiseDoubleOperator, IDifferentiable
    {
        public PowerElementWise(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)
        {
            return Power.EvaluatePower(Left, Right, this);
        }
 
        public override IElement Evaluate(double Left, double Right)
        {
            return new DoubleNumber(Math.Pow(Left, Right));
        }
 
        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 MultiplyElementWise(
                    this,
                    new Add(
                        new MultiplyElementWise(
                            Left.Differentiate(VariableName, Variables),
                            new Divide(this.right, this.left, Start, Len, Expression),
                            Start, Len, Expression),
                        new MultiplyElementWise(
                            Right.Differentiate(VariableName, Variables),
                            new Ln(this.left, Start, Len, Expression),
                            Start, Len, Expression),
                        Start, Len, Expression),
                    Start, Len, Expression);
            }
            else
                throw new ScriptRuntimeException("Operands not differentiable.", this);
        }
 
    }
}