#ifndef LEPTON_OPERATION_H_
#define LEPTON_OPERATION_H_

/* -------------------------------------------------------------------------- *
 *                                   Lepton                                   *
 * -------------------------------------------------------------------------- *
 * This is part of the Lepton expression parser originating from              *
 * Simbios, the NIH National Center for Physics-Based Simulation of           *
 * Biological Structures at Stanford, funded under the NIH Roadmap for        *
 * Medical Research, grant U54 GM072970. See https://simtk.org.               *
 *                                                                            *
 * Portions copyright (c) 2009 Stanford University and the Authors.           *
 * Authors: Peter Eastman                                                     *
 * Contributors:                                                              *
 *                                                                            *
 * Permission is hereby granted, free of charge, to any person obtaining a    *
 * copy of this software and associated documentation files (the "Software"), *
 * to deal in the Software without restriction, including without limitation  *
 * the rights to use, copy, modify, merge, publish, distribute, sublicense,   *
 * and/or sell copies of the Software, and to permit persons to whom the      *
 * Software is furnished to do so, subject to the following conditions:       *
 *                                                                            *
 * The above copyright notice and this permission notice shall be included in *
 * all copies or substantial portions of the Software.                        *
 *                                                                            *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR *
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,   *
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL    *
 * THE AUTHORS, CONTRIBUTORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM,    *
 * DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR      *
 * OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE  *
 * USE OR OTHER DEALINGS IN THE SOFTWARE.                                     *
 * -------------------------------------------------------------------------- */

#include "windowsIncludes.h"
#include "CustomFunction.h"
#include "Exception.h"
#include <cmath>
#include <map>
#include <string>
#include <vector>
#include <sstream>

namespace Lepton {

class ExpressionTreeNode;

/**
 * An Operation represents a single step in the evaluation of an expression, such as a function,
 * an operator, or a constant value.  Each Operation takes some number of values as arguments
 * and produces a single value.
 *
 * This is an abstract class with subclasses for specific operations.
 */

class LEPTON_EXPORT Operation {
public:
    virtual ~Operation() {
    }
    /**
     * This enumeration lists all Operation subclasses.  This is provided so that switch statements
     * can be used when processing or analyzing parsed expressions.
     */
    enum Id {CONSTANT, VARIABLE, CUSTOM, ADD, SUBTRACT, MULTIPLY, DIVIDE, POWER, NEGATE, SQRT, EXP, LOG,
             SIN, COS, SEC, CSC, TAN, COT, ASIN, ACOS, ATAN, SINH, COSH, TANH, STEP, SQUARE, CUBE, RECIPROCAL,
             ADD_CONSTANT, MULTIPLY_CONSTANT, POWER_CONSTANT};
    /**
     * Get the name of this Operation.
     */
    virtual std::string getName() const = 0;
    /**
     * Get this Operation's ID.
     */
    virtual Id getId() const = 0;
    /**
     * Get the number of arguments this operation expects.
     */
    virtual int getNumArguments() const = 0;
    /**
     * Create a clone of this Operation.
     */
    virtual Operation* clone() const = 0;
    /**
     * Perform the computation represented by this operation.
     *
     * @param args        the array of arguments
     * @param variables   a map containing the values of all variables
     * @return the result of performing the computation.
     */
    virtual double evaluate(double* args, const std::map<std::string, double>& variables) const = 0;
    /**
     * Return an ExpressionTreeNode which represents the analytic derivative of this Operation with respect to a variable.
     *
     * @param children     the child nodes
     * @param childDerivs  the derivatives of the child nodes with respect to the variable
     * @param variable     the variable with respect to which the derivate should be taken
     */
    virtual ExpressionTreeNode differentiate(const std::vector<ExpressionTreeNode>& children, const std::vector<ExpressionTreeNode>& childDerivs, const std::string& variable) const = 0;
    /**
     * Get whether this operation should be displayed with infix notation.
     */
    virtual bool isInfixOperator() const {
        return false;
    }
    virtual bool operator!=(const Operation& op) const {
        return op.getId() != getId();
    }
    virtual bool operator==(const Operation& op) const {
        return !(*this != op);
    }
    class Constant;
    class Variable;
    class Custom;
    class Add;
    class Subtract;
    class Multiply;
    class Divide;
    class Power;
    class Negate;
    class Sqrt;
    class Exp;
    class Log;
    class Sin;
    class Cos;
    class Sec;
    class Csc;
    class Tan;
    class Cot;
    class Asin;
    class Acos;
    class Atan;
    class Sinh;
    class Cosh;
    class Tanh;
    class Step;
    class Square;
    class Cube;
    class Reciprocal;
    class AddConstant;
    class MultiplyConstant;
    class PowerConstant;
};

class Operation::Constant : public Operation {
public:
    Constant(double value) : value(value) {
    }
    std::string getName() const {
        std::stringstream name;
        name << value;
        return name.str();
    }
    Id getId() const {
        return CONSTANT;
    }
    int getNumArguments() const {
        return 0;
    }
    Operation* clone() const {
        return new Constant(value);
    }
    double evaluate(double* args, const std::map<std::string, double>& variables) const {
        return value;
    }
    ExpressionTreeNode differentiate(const std::vector<ExpressionTreeNode>& children, const std::vector<ExpressionTreeNode>& childDerivs, const std::string& variable) const;
    double getValue() const {
        return value;
    }
    bool operator!=(const Operation& op) const {
        const Constant* o = dynamic_cast<const Constant*>(&op);
        return (o == NULL || o->value != value);
    }
private:
    double value;
};

class Operation::Variable : public Operation {
public:
    Variable(const std::string& name) : name(name) {
    }
    std::string getName() const {
        return name;
    }
    Id getId() const {
        return VARIABLE;
    }
    int getNumArguments() const {
        return 0;
    }
    Operation* clone() const {
        return new Variable(name);
    }
    double evaluate(double* args, const std::map<std::string, double>& variables) const {
        std::map<std::string, double>::const_iterator iter = variables.find(name);
        if (iter == variables.end())
            throw Exception("No value specified for variable "+name);
        return iter->second;
    }
    ExpressionTreeNode differentiate(const std::vector<ExpressionTreeNode>& children, const std::vector<ExpressionTreeNode>& childDerivs, const std::string& variable) const;
    bool operator!=(const Operation& op) const {
        const Variable* o = dynamic_cast<const Variable*>(&op);
        return (o == NULL || o->name != name);
    }
private:
    std::string name;
};

class Operation::Custom : public Operation {
public:
    Custom(const std::string& name, CustomFunction* function) : name(name), function(function), isDerivative(false), derivOrder(function->getNumArguments(), 0) {
    }
    Custom(const Custom& base, int derivIndex) : name(base.name), function(base.function->clone()), isDerivative(true), derivOrder(base.derivOrder) {
        derivOrder[derivIndex]++;
    }
    ~Custom() {
        delete function;
    }
    std::string getName() const {
        return name;
    }
    Id getId() const {
        return CUSTOM;
    }
    int getNumArguments() const {
        return function->getNumArguments();
    }
    Operation* clone() const {
        Custom* clone = new Custom(name, function->clone());
        clone->isDerivative = isDerivative;
        clone->derivOrder = derivOrder;
        return clone;
    }
    double evaluate(double* args, const std::map<std::string, double>& variables) const {
        if (isDerivative)
            return function->evaluateDerivative(args, &derivOrder[0]);
        return function->evaluate(args);
    }
    ExpressionTreeNode differentiate(const std::vector<ExpressionTreeNode>& children, const std::vector<ExpressionTreeNode>& childDerivs, const std::string& variable) const;
    const std::vector<int>& getDerivOrder() const {
        return derivOrder;
    }
    bool operator!=(const Operation& op) const {
        const Custom* o = dynamic_cast<const Custom*>(&op);
        return (o == NULL || o->name != name || o->isDerivative != isDerivative || o->derivOrder != derivOrder);
    }
private:
    std::string name;
    CustomFunction* function;
    bool isDerivative;
    std::vector<int> derivOrder;
};

class Operation::Add : public Operation {
public:
    Add() {
    }
    std::string getName() const {
        return "+";
    }
    Id getId() const {
        return ADD;
    }
    int getNumArguments() const {
        return 2;
    }
    Operation* clone() const {
        return new Add();
    }
    double evaluate(double* args, const std::map<std::string, double>& variables) const {
        return args[0]+args[1];
    }
    ExpressionTreeNode differentiate(const std::vector<ExpressionTreeNode>& children, const std::vector<ExpressionTreeNode>& childDerivs, const std::string& variable) const;
    bool isInfixOperator() const {
        return true;
    }
};

class Operation::Subtract : public Operation {
public:
    Subtract() {
    }
    std::string getName() const {
        return "-";
    }
    Id getId() const {
        return SUBTRACT;
    }
    int getNumArguments() const {
        return 2;
    }
    Operation* clone() const {
        return new Subtract();
    }
    double evaluate(double* args, const std::map<std::string, double>& variables) const {
        return args[0]-args[1];
    }
    ExpressionTreeNode differentiate(const std::vector<ExpressionTreeNode>& children, const std::vector<ExpressionTreeNode>& childDerivs, const std::string& variable) const;
    bool isInfixOperator() const {
        return true;
    }
};

class Operation::Multiply : public Operation {
public:
    Multiply() {
    }
    std::string getName() const {
        return "*";
    }
    Id getId() const {
        return MULTIPLY;
    }
    int getNumArguments() const {
        return 2;
    }
    Operation* clone() const {
        return new Multiply();
    }
    double evaluate(double* args, const std::map<std::string, double>& variables) const {
        return args[0]*args[1];
    }
    ExpressionTreeNode differentiate(const std::vector<ExpressionTreeNode>& children, const std::vector<ExpressionTreeNode>& childDerivs, const std::string& variable) const;
    bool isInfixOperator() const {
        return true;
    }
};

class Operation::Divide : public Operation {
public:
    Divide() {
    }
    std::string getName() const {
        return "/";
    }
    Id getId() const {
        return DIVIDE;
    }
    int getNumArguments() const {
        return 2;
    }
    Operation* clone() const {
        return new Divide();
    }
    double evaluate(double* args, const std::map<std::string, double>& variables) const {
        return args[0]/args[1];
    }
    ExpressionTreeNode differentiate(const std::vector<ExpressionTreeNode>& children, const std::vector<ExpressionTreeNode>& childDerivs, const std::string& variable) const;
    bool isInfixOperator() const {
        return true;
    }
};

class Operation::Power : public Operation {
public:
    Power() {
    }
    std::string getName() const {
        return "^";
    }
    Id getId() const {
        return POWER;
    }
    int getNumArguments() const {
        return 2;
    }
    Operation* clone() const {
        return new Power();
    }
    double evaluate(double* args, const std::map<std::string, double>& variables) const {
        return std::pow(args[0], args[1]);
    }
    ExpressionTreeNode differentiate(const std::vector<ExpressionTreeNode>& children, const std::vector<ExpressionTreeNode>& childDerivs, const std::string& variable) const;
    bool isInfixOperator() const {
        return true;
    }
};

class Operation::Negate : public Operation {
public:
    Negate() {
    }
    std::string getName() const {
        return "-";
    }
    Id getId() const {
        return NEGATE;
    }
    int getNumArguments() const {
        return 1;
    }
    Operation* clone() const {
        return new Negate();
    }
    double evaluate(double* args, const std::map<std::string, double>& variables) const {
        return -args[0];
    }
    ExpressionTreeNode differentiate(const std::vector<ExpressionTreeNode>& children, const std::vector<ExpressionTreeNode>& childDerivs, const std::string& variable) const;
};

class Operation::Sqrt : public Operation {
public:
    Sqrt() {
    }
    std::string getName() const {
        return "sqrt";
    }
    Id getId() const {
        return SQRT;
    }
    int getNumArguments() const {
        return 1;
    }
    Operation* clone() const {
        return new Sqrt();
    }
    double evaluate(double* args, const std::map<std::string, double>& variables) const {
        return std::sqrt(args[0]);
    }
    ExpressionTreeNode differentiate(const std::vector<ExpressionTreeNode>& children, const std::vector<ExpressionTreeNode>& childDerivs, const std::string& variable) const;
};

class Operation::Exp : public Operation {
public:
    Exp() {
    }
    std::string getName() const {
        return "exp";
    }
    Id getId() const {
        return EXP;
    }
    int getNumArguments() const {
        return 1;
    }
    Operation* clone() const {
        return new Exp();
    }
    double evaluate(double* args, const std::map<std::string, double>& variables) const {
        return std::exp(args[0]);
    }
    ExpressionTreeNode differentiate(const std::vector<ExpressionTreeNode>& children, const std::vector<ExpressionTreeNode>& childDerivs, const std::string& variable) const;
};

class Operation::Log : public Operation {
public:
    Log() {
    }
    std::string getName() const {
        return "log";
    }
    Id getId() const {
        return LOG;
    }
    int getNumArguments() const {
        return 1;
    }
    Operation* clone() const {
        return new Log();
    }
    double evaluate(double* args, const std::map<std::string, double>& variables) const {
        return std::log(args[0]);
    }
    ExpressionTreeNode differentiate(const std::vector<ExpressionTreeNode>& children, const std::vector<ExpressionTreeNode>& childDerivs, const std::string& variable) const;
};

class Operation::Sin : public Operation {
public:
    Sin() {
    }
    std::string getName() const {
        return "sin";
    }
    Id getId() const {
        return SIN;
    }
    int getNumArguments() const {
        return 1;
    }
    Operation* clone() const {
        return new Sin();
    }
    double evaluate(double* args, const std::map<std::string, double>& variables) const {
        return std::sin(args[0]);
    }
    ExpressionTreeNode differentiate(const std::vector<ExpressionTreeNode>& children, const std::vector<ExpressionTreeNode>& childDerivs, const std::string& variable) const;
};

class Operation::Cos : public Operation {
public:
    Cos() {
    }
    std::string getName() const {
        return "cos";
    }
    Id getId() const {
        return COS;
    }
    int getNumArguments() const {
        return 1;
    }
    Operation* clone() const {
        return new Cos();
    }
    double evaluate(double* args, const std::map<std::string, double>& variables) const {
        return std::cos(args[0]);
    }
    ExpressionTreeNode differentiate(const std::vector<ExpressionTreeNode>& children, const std::vector<ExpressionTreeNode>& childDerivs, const std::string& variable) const;
};

class Operation::Sec : public Operation {
public:
    Sec() {
    }
    std::string getName() const {
        return "sec";
    }
    Id getId() const {
        return SEC;
    }
    int getNumArguments() const {
        return 1;
    }
    Operation* clone() const {
        return new Sec();
    }
    double evaluate(double* args, const std::map<std::string, double>& variables) const {
        return 1.0/std::cos(args[0]);
    }
    ExpressionTreeNode differentiate(const std::vector<ExpressionTreeNode>& children, const std::vector<ExpressionTreeNode>& childDerivs, const std::string& variable) const;
};

class Operation::Csc : public Operation {
public:
    Csc() {
    }
    std::string getName() const {
        return "csc";
    }
    Id getId() const {
        return CSC;
    }
    int getNumArguments() const {
        return 1;
    }
    Operation* clone() const {
        return new Csc();
    }
    double evaluate(double* args, const std::map<std::string, double>& variables) const {
        return 1.0/std::sin(args[0]);
    }
    ExpressionTreeNode differentiate(const std::vector<ExpressionTreeNode>& children, const std::vector<ExpressionTreeNode>& childDerivs, const std::string& variable) const;
};

class Operation::Tan : public Operation {
public:
    Tan() {
    }
    std::string getName() const {
        return "tan";
    }
    Id getId() const {
        return TAN;
    }
    int getNumArguments() const {
        return 1;
    }
    Operation* clone() const {
        return new Tan();
    }
    double evaluate(double* args, const std::map<std::string, double>& variables) const {
        return std::tan(args[0]);
    }
    ExpressionTreeNode differentiate(const std::vector<ExpressionTreeNode>& children, const std::vector<ExpressionTreeNode>& childDerivs, const std::string& variable) const;
};

class Operation::Cot : public Operation {
public:
    Cot() {
    }
    std::string getName() const {
        return "cot";
    }
    Id getId() const {
        return COT;
    }
    int getNumArguments() const {
        return 1;
    }
    Operation* clone() const {
        return new Cot();
    }
    double evaluate(double* args, const std::map<std::string, double>& variables) const {
        return 1.0/std::tan(args[0]);
    }
    ExpressionTreeNode differentiate(const std::vector<ExpressionTreeNode>& children, const std::vector<ExpressionTreeNode>& childDerivs, const std::string& variable) const;
};

class Operation::Asin : public Operation {
public:
    Asin() {
    }
    std::string getName() const {
        return "asin";
    }
    Id getId() const {
        return ASIN;
    }
    int getNumArguments() const {
        return 1;
    }
    Operation* clone() const {
        return new Asin();
    }
    double evaluate(double* args, const std::map<std::string, double>& variables) const {
        return std::asin(args[0]);
    }
    ExpressionTreeNode differentiate(const std::vector<ExpressionTreeNode>& children, const std::vector<ExpressionTreeNode>& childDerivs, const std::string& variable) const;
};

class Operation::Acos : public Operation {
public:
    Acos() {
    }
    std::string getName() const {
        return "acos";
    }
    Id getId() const {
        return ACOS;
    }
    int getNumArguments() const {
        return 1;
    }
    Operation* clone() const {
        return new Acos();
    }
    double evaluate(double* args, const std::map<std::string, double>& variables) const {
        return std::acos(args[0]);
    }
    ExpressionTreeNode differentiate(const std::vector<ExpressionTreeNode>& children, const std::vector<ExpressionTreeNode>& childDerivs, const std::string& variable) const;
};

class Operation::Atan : public Operation {
public:
    Atan() {
    }
    std::string getName() const {
        return "atan";
    }
    Id getId() const {
        return ATAN;
    }
    int getNumArguments() const {
        return 1;
    }
    Operation* clone() const {
        return new Atan();
    }
    double evaluate(double* args, const std::map<std::string, double>& variables) const {
        return std::atan(args[0]);
    }
    ExpressionTreeNode differentiate(const std::vector<ExpressionTreeNode>& children, const std::vector<ExpressionTreeNode>& childDerivs, const std::string& variable) const;
};

class Operation::Sinh : public Operation {
public:
    Sinh() {
    }
    std::string getName() const {
        return "sinh";
    }
    Id getId() const {
        return SINH;
    }
    int getNumArguments() const {
        return 1;
    }
    Operation* clone() const {
        return new Sinh();
    }
    double evaluate(double* args, const std::map<std::string, double>& variables) const {
        return std::sinh(args[0]);
    }
    ExpressionTreeNode differentiate(const std::vector<ExpressionTreeNode>& children, const std::vector<ExpressionTreeNode>& childDerivs, const std::string& variable) const;
};

class Operation::Cosh : public Operation {
public:
    Cosh() {
    }
    std::string getName() const {
        return "cosh";
    }
    Id getId() const {
        return COSH;
    }
    int getNumArguments() const {
        return 1;
    }
    Operation* clone() const {
        return new Cosh();
    }
    double evaluate(double* args, const std::map<std::string, double>& variables) const {
        return std::cosh(args[0]);
    }
    ExpressionTreeNode differentiate(const std::vector<ExpressionTreeNode>& children, const std::vector<ExpressionTreeNode>& childDerivs, const std::string& variable) const;
};

class Operation::Tanh : public Operation {
public:
    Tanh() {
    }
    std::string getName() const {
        return "tanh";
    }
    Id getId() const {
        return TANH;
    }
    int getNumArguments() const {
        return 1;
    }
    Operation* clone() const {
        return new Tanh();
    }
    double evaluate(double* args, const std::map<std::string, double>& variables) const {
        return std::tanh(args[0]);
    }
    ExpressionTreeNode differentiate(const std::vector<ExpressionTreeNode>& children, const std::vector<ExpressionTreeNode>& childDerivs, const std::string& variable) const;
};

class Operation::Step : public Operation {
public:
    Step() {
    }
    std::string getName() const {
        return "step";
    }
    Id getId() const {
        return STEP;
    }
    int getNumArguments() const {
        return 1;
    }
    Operation* clone() const {
        return new Step();
    }
    double evaluate(double* args, const std::map<std::string, double>& variables) const {
        return (args[0] >= 0.0 ? 1.0 : 0.0);
    }
    ExpressionTreeNode differentiate(const std::vector<ExpressionTreeNode>& children, const std::vector<ExpressionTreeNode>& childDerivs, const std::string& variable) const;
};

class Operation::Square : public Operation {
public:
    Square() {
    }
    std::string getName() const {
        return "square";
    }
    Id getId() const {
        return SQUARE;
    }
    int getNumArguments() const {
        return 1;
    }
    Operation* clone() const {
        return new Square();
    }
    double evaluate(double* args, const std::map<std::string, double>& variables) const {
        return args[0]*args[0];
    }
    ExpressionTreeNode differentiate(const std::vector<ExpressionTreeNode>& children, const std::vector<ExpressionTreeNode>& childDerivs, const std::string& variable) const;
};

class Operation::Cube : public Operation {
public:
    Cube() {
    }
    std::string getName() const {
        return "cube";
    }
    Id getId() const {
        return CUBE;
    }
    int getNumArguments() const {
        return 1;
    }
    Operation* clone() const {
        return new Cube();
    }
    double evaluate(double* args, const std::map<std::string, double>& variables) const {
        return args[0]*args[0]*args[0];
    }
    ExpressionTreeNode differentiate(const std::vector<ExpressionTreeNode>& children, const std::vector<ExpressionTreeNode>& childDerivs, const std::string& variable) const;
};

class Operation::Reciprocal : public Operation {
public:
    Reciprocal() {
    }
    std::string getName() const {
        return "recip";
    }
    Id getId() const {
        return RECIPROCAL;
    }
    int getNumArguments() const {
        return 1;
    }
    Operation* clone() const {
        return new Reciprocal();
    }
    double evaluate(double* args, const std::map<std::string, double>& variables) const {
        return 1.0/args[0];
    }
    ExpressionTreeNode differentiate(const std::vector<ExpressionTreeNode>& children, const std::vector<ExpressionTreeNode>& childDerivs, const std::string& variable) const;
};

class Operation::AddConstant : public Operation {
public:
    AddConstant(double value) : value(value) {
    }
    std::string getName() const {
        std::stringstream name;
        name << value << "+";
        return name.str();
    }
    Id getId() const {
        return ADD_CONSTANT;
    }
    int getNumArguments() const {
        return 1;
    }
    Operation* clone() const {
        return new AddConstant(value);
    }
    double evaluate(double* args, const std::map<std::string, double>& variables) const {
        return args[0]+value;
    }
    ExpressionTreeNode differentiate(const std::vector<ExpressionTreeNode>& children, const std::vector<ExpressionTreeNode>& childDerivs, const std::string& variable) const;
    double getValue() const {
        return value;
    }
    bool operator!=(const Operation& op) const {
        const AddConstant* o = dynamic_cast<const AddConstant*>(&op);
        return (o == NULL || o->value != value);
    }
private:
    double value;
};

class Operation::MultiplyConstant : public Operation {
public:
    MultiplyConstant(double value) : value(value) {
    }
    std::string getName() const {
        std::stringstream name;
        name << value << "*";
        return name.str();
    }
    Id getId() const {
        return MULTIPLY_CONSTANT;
    }
    int getNumArguments() const {
        return 1;
    }
    Operation* clone() const {
        return new MultiplyConstant(value);
    }
    double evaluate(double* args, const std::map<std::string, double>& variables) const {
        return args[0]*value;
    }
    ExpressionTreeNode differentiate(const std::vector<ExpressionTreeNode>& children, const std::vector<ExpressionTreeNode>& childDerivs, const std::string& variable) const;
    double getValue() const {
        return value;
    }
    bool operator!=(const Operation& op) const {
        const MultiplyConstant* o = dynamic_cast<const MultiplyConstant*>(&op);
        return (o == NULL || o->value != value);
    }
private:
    double value;
};

class Operation::PowerConstant : public Operation {
public:
    PowerConstant(double value) : value(value) {
    }
    std::string getName() const {
        std::stringstream name;
        name << "^" << value;
        return name.str();
    }
    Id getId() const {
        return POWER_CONSTANT;
    }
    int getNumArguments() const {
        return 1;
    }
    Operation* clone() const {
        return new PowerConstant(value);
    }
    double evaluate(double* args, const std::map<std::string, double>& variables) const {
        return std::pow(args[0], value);
    }
    ExpressionTreeNode differentiate(const std::vector<ExpressionTreeNode>& children, const std::vector<ExpressionTreeNode>& childDerivs, const std::string& variable) const;
    double getValue() const {
        return value;
    }
    bool operator!=(const Operation& op) const {
        const PowerConstant* o = dynamic_cast<const PowerConstant*>(&op);
        return (o == NULL || o->value != value);
    }
private:
    double value;
};

} // namespace Lepton

#endif /*LEPTON_OPERATION_H_*/
