tempest/src/storm/storage/expressions/RationalFunctionToExpression.cpp

//
// Created by Jip Spel on 24.09.18.
//

#include "RationalFunctionToExpression.h"
#include "storm/utility/constants.h"

namespace storm {
    namespace expressions {
        template <typename ValueType>
        RationalFunctionToExpression<ValueType>::RationalFunctionToExpression(std::shared_ptr<ExpressionManager> manager) : manager(manager) {
            // Intentionally left empty.
        }

        template <typename ValueType>
        std::shared_ptr<ExpressionManager> RationalFunctionToExpression<ValueType>::getManager()  {
            return manager;
        }

        template <typename ValueType>
        Expression RationalFunctionToExpression<ValueType>::toExpression(ValueType function) {
            function.simplify();
            auto varsFunction = function.gatherVariables();
            for (auto var : varsFunction) {
                auto varsManager = manager->getVariables();
                bool found = find_if(varsManager.begin(), varsManager.end(),
                                     [&](auto val) -> bool {
                                        return val.getName() == var.name();
                                     }) != varsManager.end();
                if (!found) {
                    manager->declareRationalVariable(var.name());
                }
            }

            auto denominator = function.denominator();
            if (!denominator.isConstant()) {
                STORM_LOG_DEBUG("Expecting the denominator to be constant");
            }

            storm::expressions::Expression result;
            if (function.isConstant()) {
                result = manager->rational(storm::utility::convertNumber<storm::RationalNumber, storm::RationalFunctionCoefficient>(function.constantPart()));
            } else {
                auto nominator = function.nominatorAsPolynomial().polynomialWithCoefficient();
                result = manager->rational(storm::utility::convertNumber<storm::RationalNumber, storm::RationalFunctionCoefficient>(nominator.constantPart()));
                for (auto itr = nominator.begin(); itr != nominator.end(); ++itr) {
                    varsFunction.clear();
                    itr->gatherVariables(varsFunction);

                    storm::expressions::Expression nominatorPartExpr = manager->rational(storm::utility::convertNumber<storm::RationalNumber, storm::RationalFunctionCoefficient>(itr->coeff()));
                    for (auto var : varsFunction) {
                        nominatorPartExpr = nominatorPartExpr * storm::expressions::pow(manager->getVariable(var.name()), manager->rational(storm::utility::convertNumber<storm::RationalNumber, storm::RationalFunctionCoefficient>(itr->monomial()->exponentOfVariable(var))));
                    }
                    if (varsFunction.size() >= 1) {
                        result = result + nominatorPartExpr;
                    }
                }
                storm::expressions::Expression denominatorVal = manager->rational(storm::utility::convertNumber<storm::RationalNumber, storm::RationalFunctionCoefficient>(denominator.constantPart()));
                result = result / denominatorVal;
            }

            return result;
        }

        template class RationalFunctionToExpression<storm::RationalFunction>;
    }
}