Quantity.h

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/* Copyright 2019 Kristofer Björnson
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

#ifndef COM_DAFER45_TBTK_QUANTITY_QUANTITY
#define COM_DAFER45_TBTK_QUANTITY_QUANTITY

#include "TBTK/Real.h"
#include "TBTK/TBTKMacros.h"

#include <map>
#include <string>

namespace TBTK{
namespace Quantity{

template<typename Units, typename Exponents>
class Quantity : public Real{
public:
    using Unit = Units;
    using Exponent = Exponents;

    Quantity(){};

    Quantity(double value) : Real(value){};

    static std::string getUnitString(Unit unit);

    static Unit getUnit(const std::string &unit);

    static double getConversionFactor(Unit unit);
protected:
    static class ConversionTable{
    public:
        std::map<Unit, std::string> unitToString;
        std::map<std::string, Unit> stringToUnit;
        std::map<Unit, double> conversionFactors;

        ConversionTable(
            const std::map<
                Unit,
                std::pair<std::string, double>
            > &conversionTable
        ){
            for(auto entry : conversionTable){
                unitToString[entry.first] = entry.second.first;
                stringToUnit[entry.second.first] = entry.first;
                conversionFactors[entry.first]
                    = entry.second.second;
            }
        }
    } conversionTable;
};

template<typename Units, typename Exponents>
std::string Quantity<Units, Exponents>::getUnitString(Unit unit){
    try{
        return conversionTable.unitToString.at(unit);
    }
    catch(const std::out_of_range &e){
        TBTKExit(
            "Quantity::getUnitString()",
            "Unknown unit '" << static_cast<int>(unit) << "'.",
            ""
        );
        return "";
    }
}

template<typename Units, typename Exponents>
typename Quantity<Units, Exponents>::Unit Quantity<Units, Exponents>::getUnit(
    const std::string &unit
){
    try{
        return conversionTable.stringToUnit.at(unit);
    }
    catch(const std::out_of_range &e){
        TBTKExit(
            "Quantity::getUnit()",
            "Unknown unit '" << unit << "'.",
            ""
        );
    }
}

template<typename Units, typename Exponents>
double Quantity<Units, Exponents>::getConversionFactor(Unit unit){
    try{
        return conversionTable.conversionFactors.at(unit);
    }
    catch(const std::out_of_range &e){
        TBTKExit(
            "Quantity::getConversionFactor()",
            "Unknown unit '" << static_cast<int>(unit) << "'.",
            ""
        );
    }
}

}; //End of namesapce Quantity
}; //End of namesapce TBTK

#endif