//******************************************************************************
//** SCATMECH: Polarized Light Scattering C++ Class Library
//** 
//** File: scateval.h
//**
//** Thomas A. Germer
//** Optical Technology Division, National Institute of Standards and Technology
//** 100 Bureau Dr. Stop 8443; Gaithersburg, MD 20899-8443
//** Phone: (301) 975-2876; FAX: (301) 975-6991
//** Email: thomas.germer@nist.gov
//**
//** Version: 6.00 (February 2008)
//**
//******************************************************************************
#ifndef SCATMECH_SCATEVAL_H
#define SCATMECH_SCATEVAL_H

#include "scatmech.h"
#include <string>
#include <stack>
#include <vector>
#include <sstream>
#include <map>

namespace SCATMECH {

    /// @brief A class for evaluating expressions
    ///
    /// A class that takes a string expression (e.g., "3+4*x") and evaluates
    /// it using an optional list of variables.  Results can be multiple
    /// values separated by commas and surrounded by parentheses.
    class Evaluator {
    public:

        /// A vector of doubles
        typedef std::vector<double> VDOUBLE;

        /// A string
        typedef std::string STRING;

        /// A map from a string to a double
        typedef std::map<STRING,double> VMAP;

        /// Constructor
        Evaluator(const STRING& str,                 ///< Expression to evaluate
                  const VMAP& _variables = VMAP(),   ///< Map of variables
                  bool _top=true                     ///< Normally true, but false for recursive calls
                  ) : input(str), variables(_variables), top(_top) {evaluate();}

        /// Get the result, forcing it to have only one value.
        operator double() const {
            if (result.size()!=1) error("Call to double() with more than one value");
            return result[0];
        }

        /// Get the result as a character string
        STRING ResultString() const;

        /// Get the i-th result
        double Result(int i) {return result[i];}

        /// Get the number of results
        int NResult() {return result.size();}
        
    private:

        const VMAP& variables;  

        std::istringstream input;      
        std::stack<double> val_stack;
        std::stack<int> op_stack;
        std::stack<int> prec_stack;
        VDOUBLE result;

        void evaluate();
        void operate();
        double call_function(const STRING& s,const VDOUBLE& args);
        void error(const std::string& message) const;
        bool lower_prec(int prec);
        void get_value();
        void get_operator();
        VDOUBLE get_paren(bool allow_empty=false);

        bool top;
    }; 

}

#endif