Trace.cs

using System;
using Waher.Script.Abstraction.Elements;
using Waher.Script.Exceptions;
using Waher.Script.Functions.Vectors;
using Waher.Script.Model;
 
namespace Waher.Script.Functions.Matrices
{
    public class Trace : FunctionOneVariable
    {
        public Trace(ScriptNode Argument, int Start, int Length, Expression Expression)
            : base(Argument, Start, Length, Expression)
        {
        }
 
        public override string FunctionName => nameof(Trace);
 
        public override string[] Aliases => new string[] { "tr" };
 
        public override IElement Evaluate(IElement Argument, Variables Variables)
        {
            if (Argument is IMatrix M)
            {
                int N = Math.Min(M.Columns, M.Rows);
                IElement[] Elements = new IElement[N];
                int i;
 
                for (i = 0; i < N; i++)
                    Elements[i] = M.GetElement(i, i);
 
                return Sum.EvaluateSum(Elements, this);
            }
            else
                throw new ScriptRuntimeException("Expected matrix argument.", this);
        }
    }
}