private NonlinearEquationDescription CompileEquations(RootNode root)
        {
            List <RPNExpression>         rpnEquations = new List <RPNExpression>();
            List <Expression.Expression> equations    = new List <Expression.Expression>();

            foreach (var constant in root.constants)
            {
                Expression.Expression right = ExpressionSimplifier.Simplify(ConvertToExpression(constant.Right));
                //ExpressionNode right = simplify(constant.Right);
                if (right is Float)
                {
                    constants.Add(constant.Identifier, ((Float)right).Value);
                }
                else
                {
                    constants.Add(constant.Identifier, float.NaN);
                    compilerErrors.Add(new ErrorMessage("Определение константы " + constant.Identifier + " не является константным выражением"));
                }
            }

            foreach (var equation in root.equations)
            {
                SubtractionNode subtraction = new SubtractionNode
                {
                    Left     = equation.Left,
                    Right    = equation.Right,
                    Line     = equation.Line,
                    Position = equation.Position
                };
                Expression.Expression expression = ExpressionSimplifier.Simplify(ConvertToExpression(subtraction));
                equations.Add(expression);
            }

            //initialValues aren't important
            foreach (var initialValue in root.initialValues)
            {
                if (variables.ContainsKey(initialValue.Identifier))
                {
                    Expression.Expression right = ExpressionSimplifier.Simplify(ConvertToExpression(initialValue.Right));
                    //Expression expression = ConvertToExpression(right)
                    if (right is Float)
                    {
                        initialValues[variables[initialValue.Identifier]] = ((Float)right).Value;
                    }
                    else
                    {
                        //add error message
                        compilerErrors.Add(new ErrorMessage("Определение начального приближения переменной" +
                                                            initialValue.Identifier + " не является константным выражением"));
                    }
                }
                else
                {
                    //add error message
                    compilerErrors.Add(new ErrorMessage("Определение начального приближения несуществующей переменной"));
                }
            }
            //check that number of variables = number of equations
            if (variableNames.Count != equations.Count)
            {
                compilerErrors.Add(new ErrorMessage($"Количество переменных не совпадает с количеством уравнений: {variableNames.Count} переменных, {equations.Count} уравнений"));
            }
            if (equations.Count == 0)
            {
                compilerErrors.Add(new ErrorMessage("Пустая система уравнений"));
            }
            if (compilerErrors.Count > 0)
            {
                throw new CompilerException(compilerErrors);
                //fall back;
            }
            Expression.Compiler expCompiler = new Expression.Compiler(variables);
            for (int i = 0; i < equations.Count; i++)
            {
                rpnEquations.Add(expCompiler.Compile(equations[i]));
            }
            RPNExpression [,] jacobiMatrix = new RPNExpression[equations.Count, equations.Count];
            Expression.DifferentiationVisitor difVisitor = new Expression.DifferentiationVisitor();
            int j = 0;

            foreach (var equation in equations)
            {
                int i = 0;
                foreach (var variable in variableNames)
                {
                    //find derivative for variable
                    Expression.Expression derivative = ExpressionSimplifier.Simplify(difVisitor.Differentiate(equation, variable));
                    //simplify derivative expression
                    RPNExpression exp = expCompiler.Compile(derivative);
                    jacobiMatrix[i, j] = exp;
                    i++;
                }
                j++;
            }
            NonlinearEquationDescription ned = new NonlinearEquationDescription(initialValues.ToArray(), variableNames.ToArray(),
                                                                                rpnEquations, jacobiMatrix);

            return(ned);
        }
        private Implicit.DAEIDescription CompileDAEImplicit(RootNode root)
        {
            List <Expression.Expression> equations = new List <Expression.Expression>();

            constants["time"] = 1.0;
            constants["t0"]   = 0.0;
            foreach (var constant in root.constants)
            {
                //Convert to expression
                Expression.Expression right = ExpressionSimplifier.Simplify(ConvertToExpression(constant.Right));
                if (right is Float)
                {
                    constants[constant.Identifier] = ((Float)right).Value;
                }
                else
                {
                    constants.Add(constant.Identifier, float.NaN);
                    compilerErrors.Add(new ErrorMessage("Определение константы " + constant.Identifier + " не является константным выражением"));
                }
            }
            foreach (var parameter in root.parameters)
            {
                //Convert to expression
                Expression.Expression right = ExpressionSimplifier.Simplify(ConvertToExpression(parameter.Right));
                if (right is Float)
                {
                    //parameters.Add(parameter.Identifier, ((Float)right).Value);
                    parameters[parameter.Identifier] = ((Float)right).Value;
                }
                else
                {
                    parameters.Add(parameter.Identifier, float.NaN);
                    compilerErrors.Add(new ErrorMessage("Определение параметра " + parameter.Identifier + " не является константным выражением"));
                }
            }
            foreach (var equation in root.equations)
            {
                //Convert to expression
                SubtractionNode exp = new SubtractionNode
                {
                    Left     = equation.Left,
                    Right    = equation.Right,
                    Line     = equation.Line,
                    Position = equation.Position
                };
                Expression.Expression expression = ExpressionSimplifier.Simplify(ConvertToExpression(exp));
                equations.Add(expression);
            }
            foreach (var initialValue in root.initialValues)
            {
                if (variables.ContainsKey(initialValue.Identifier))
                {
                    //Convert to expression
                    Expression.Expression right = ExpressionSimplifier.Simplify(ConvertToExpression(initialValue.Right));
                    if (right is Float)
                    {
                        Variable var = variables[initialValue.Identifier];
                        var.InitialValue = ((Float)right).Value;
                        var.Initialized  = true;
                    }
                    else
                    {
                        //add error message
                        compilerErrors.Add(new ErrorMessage("Определение начального условия переменной " +
                                                            initialValue.Identifier + " не является константным выражением"));
                    }
                }
                else
                {
                    //add error message
                    compilerErrors.Add(new ErrorMessage("Определение начального условия несуществующей переменной"));
                }
            }

            //!!!!!!!!!!!!!!!!!!!!!!!!!

            //check that number of variables = number of equations
            if (variables.Count != equations.Count)
            {
                compilerErrors.Add(new ErrorMessage("Количество переменных не совпадает с количеством уравнений"));
            }
            if (equations.Count == 0)
            {
                compilerErrors.Add(new ErrorMessage("Пустая система уравнений"));
            }
            foreach (var variable in variables)
            {
                if (variable.Value.Initialized == false)
                {
                    variable.Value.InitialValue = 0.0;
                    //compilerErrors.Add(new ErrorMessage("Не объявлены начальные условия для переменной " + variable.Key));
                }
            }
            if (compilerErrors.Count > 0)
            {
                throw new CompilerException(compilerErrors);
                //fall back;
            }

            List <RPNExpression>     equationsRPN   = new List <RPNExpression>();
            List <string>            variableNames  = new List <string>();
            List <string>            symbolNames    = new List <string>();
            List <double>            initialValues  = new List <double>();
            Dictionary <string, int> symbolIndicies = new Dictionary <string, int>();

            List <Variable> variableList = new List <Variable>();

            foreach (var variable in variables)
            {
                variableList.Add(variable.Value);
            }
            variableList.Sort(delegate(Variable x, Variable y)
            {
                return(x.Name.CompareTo(y.Name));
            });
            //time variable
            symbolIndicies.Add("t", 0);

            symbolNames.Add("t");
            //variables
            foreach (var variable in variableList)
            {
                variableNames.Add(variable.Name);
                symbolNames.Add(variable.Name);
                initialValues.Add(variable.InitialValue);
                symbolIndicies.Add(variable.Name, symbolIndicies.Count);
            }
            //derivatives
            foreach (var variable in variableList)
            {
                symbolNames.Add(variable.Name + "'");
                symbolIndicies.Add(variable.Name + "'", symbolIndicies.Count);
            }

            string[] parameterNames  = new string[parameters.Count];
            double[] parameterValues = new double[parameters.Count];
            {
                int i = 0;
                foreach (var parameter in parameters)
                {
                    parameterNames[i]  = parameter.Key;
                    parameterValues[i] = parameter.Value;
                    i++;
                }
            }
            foreach (var parameter in parameterNames)
            {
                symbolNames.Add(parameter);
                symbolIndicies.Add(parameter, symbolIndicies.Count);
            }

            Expression.Compiler expCompiler = new Expression.Compiler(symbolIndicies);
            for (int i = 0; i < equations.Count; i++)
            {
                equationsRPN.Add(expCompiler.Compile(equations[i]));
            }
            MathUtils.SparseMatrix <RPNExpression> dfdx = MathUtils.SparseMatrix <RPNExpression> .Build(equations.Count, equations.Count);

            MathUtils.SparseMatrix <RPNExpression> dfddx = MathUtils.SparseMatrix <RPNExpression> .Build(equations.Count, equations.Count);

            Expression.DifferentiationVisitor difVisitor = new Expression.DifferentiationVisitor();
            for (int j = 0; j < equations.Count; j++)
            {
                for (int i = 0; i < equations.Count; i++)
                {
                    Expression.Expression derivative = ExpressionSimplifier.Simplify(difVisitor.Differentiate(equations[i], variableNames[j]));
                    if (derivative.Type == ExpressionType.Float)
                    {
                        if ((derivative as Expression.Float).IsZero())
                        {
                            continue;
                        }
                    }
                    RPNExpression exp = expCompiler.Compile(derivative);
                    //dfdx[i, j] = exp;
                    dfdx.Add(i, j, exp);
                }
            }
            for (int j = 0; j < equations.Count; j++)
            {
                for (int i = 0; i < equations.Count; i++)
                {
                    Expression.Expression derivative = ExpressionSimplifier.Simplify(difVisitor.Differentiate(equations[i], variableNames[j] + "'"));
                    if (derivative.Type == ExpressionType.Float)
                    {
                        if ((derivative as Expression.Float).IsZero())
                        {
                            continue;
                        }
                    }
                    RPNExpression exp = expCompiler.Compile(derivative);
                    //dfddx[i, j] = exp;
                    dfddx.Add(i, j, exp);
                }
            }
            Implicit.DAEIDescription definition = new Implicit.DAEIDescription(variableNames.ToArray(),
                                                                               parameterNames,
                                                                               parameterValues,
                                                                               initialValues.ToArray(),
                                                                               equationsRPN,
                                                                               dfdx,
                                                                               dfddx,
                                                                               constants["t0"],
                                                                               constants["time"]);
            return(definition);
        }