BinaryExpression.hpp

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//
// Created by Matthew McCall on 7/2/23.
//
 
#ifndef OASIS_BINARYEXPRESSION_HPP
#define OASIS_BINARYEXPRESSION_HPP
 
#include <algorithm>
#include <cassert>
#include <functional>
#include <list>
 
#include "Expression.hpp"
#include "RecursiveCast.hpp"
#include "Visit.hpp"
 
namespace Oasis {
template <typename MostSigOpT, typename LeastSigOpT, typename T>
concept IOperand = std::is_same_v<T, MostSigOpT> || std::is_same_v<T, LeastSigOpT>;
 
template <template <typename, typename> typename T>
concept IAssociativeAndCommutative = IExpression<T<Expression, Expression>> && ((T<Expression, Expression>::GetStaticCategory() & (Associative | Commutative)) == (Associative | Commutative));
 
template <template <typename, typename> typename T>
    requires IAssociativeAndCommutative<T>
auto BuildFromVector(const std::vector<std::unique_ptr<Expression>>& ops) -> std::unique_ptr<T<Expression, Expression>>
{
    if (ops.size() <= 1) {
        return nullptr;
    }
 
    using GeneralizedT = T<Expression, Expression>;
 
    std::list<std::unique_ptr<Expression>> opsList;
    opsList.resize(ops.size());
 
    std::transform(ops.begin(), ops.end(), opsList.begin(), [](const auto& op) { return op->Copy(); });
 
    while (std::next(opsList.begin()) != opsList.end()) {
        for (auto i = opsList.begin(); i != opsList.end() && std::next(i) != opsList.end();) {
            auto node = std::make_unique<GeneralizedT>(**i, **std::next(i));
            opsList.insert(i, std::move(node));
            i = opsList.erase(i, std::next(i, 2));
        }
    }
 
    auto* result = dynamic_cast<GeneralizedT*>(opsList.front().release());
    return std::unique_ptr<GeneralizedT>(result);
}
 
template <template <IExpression, IExpression> class DerivedT, IExpression MostSigOpT = Expression, IExpression LeastSigOpT = MostSigOpT>
class BinaryExpression : public Expression {
 
    using DerivedSpecialized = DerivedT<MostSigOpT, LeastSigOpT>;
    using DerivedGeneralized = DerivedT<Expression, Expression>;
 
public:
    BinaryExpression() = default;
    BinaryExpression(const BinaryExpression& other)
    {
        if (other.HasMostSigOp()) {
            SetMostSigOp(other.GetMostSigOp());
        }
 
        if (other.HasLeastSigOp()) {
            SetLeastSigOp(other.GetLeastSigOp());
        }
    }
 
    BinaryExpression(const MostSigOpT& mostSigOp, const LeastSigOpT& leastSigOp)
    {
        SetMostSigOp(mostSigOp);
        SetLeastSigOp(leastSigOp);
    }
 
    template <IExpression Op1T, IExpression Op2T, IExpression... OpsT>
    BinaryExpression(const Op1T& op1, const Op2T& op2, const OpsT&... ops)
    {
        static_assert(IAssociativeAndCommutative<DerivedT>, "List initializer only supported for associative and commutative expressions");
        static_assert(std::is_same_v<DerivedGeneralized, DerivedSpecialized>, "List initializer only supported for generalized expressions");
 
        std::vector<std::unique_ptr<Expression>> opsVec;
 
        for (auto opWrapper : std::vector<std::reference_wrapper<const Expression>> { static_cast<const Expression&>(op1), static_cast<const Expression&>(op2), (static_cast<const Expression&>(ops))... }) {
            const Expression& operand = opWrapper.get();
            opsVec.emplace_back(operand.Copy());
        }
 
        // build expression from vector
        auto generalized = BuildFromVector<DerivedT>(opsVec);
 
        SetLeastSigOp(generalized->GetLeastSigOp());
        SetMostSigOp(generalized->GetMostSigOp());
    }
 
    [[nodiscard]] auto Copy() const -> std::unique_ptr<Expression> final
    {
        return std::make_unique<DerivedSpecialized>(*static_cast<const DerivedSpecialized*>(this));
    }
 
    [[nodiscard]] auto Differentiate(const Expression& differentiationVariable) const -> std::unique_ptr<Expression> override
    {
        return Generalize()->Differentiate(differentiationVariable);
    }
    [[nodiscard]] auto Equals(const Expression& other) const -> bool final
    {
        if (this->GetType() != other.GetType()) {
            return false;
        }
 
        const auto otherGeneralized = other.Generalize();
        const auto& otherBinaryGeneralized = static_cast<const DerivedGeneralized&>(*otherGeneralized);
 
        bool mostSigOpMismatch = false, leastSigOpMismatch = false;
 
        if (this->HasMostSigOp() == otherBinaryGeneralized.HasMostSigOp()) {
            if (mostSigOp && otherBinaryGeneralized.HasMostSigOp()) {
                mostSigOpMismatch = !mostSigOp->Equals(otherBinaryGeneralized.GetMostSigOp());
            }
        } else {
            mostSigOpMismatch = true;
        }
 
        if (this->HasLeastSigOp() == otherBinaryGeneralized.HasLeastSigOp()) {
            if (this->HasLeastSigOp() && otherBinaryGeneralized.HasLeastSigOp()) {
                leastSigOpMismatch = !leastSigOp->Equals(otherBinaryGeneralized.GetLeastSigOp());
            }
        } else {
            mostSigOpMismatch = true;
        }
 
        if (!mostSigOpMismatch && !leastSigOpMismatch) {
            return true;
        }
 
        if (!(this->GetCategory() & Associative)) {
            return false;
        }
 
        auto thisFlattened = std::vector<std::unique_ptr<Expression>> {};
        auto otherFlattened = std::vector<std::unique_ptr<Expression>> {};
 
        this->Flatten(thisFlattened);
        otherBinaryGeneralized.Flatten(otherFlattened);
 
        for (const auto& thisOperand : thisFlattened) {
            if (std::find_if(otherFlattened.begin(), otherFlattened.end(), [&thisOperand](const auto& otherOperand) {
                    return thisOperand->Equals(*otherOperand);
                })
                == otherFlattened.end()) {
                return false;
            }
        }
 
        return true;
    }
 
    [[nodiscard]] auto Generalize() const -> std::unique_ptr<Expression> final
    {
        DerivedGeneralized generalized;
 
        if (this->mostSigOp) {
            generalized.SetMostSigOp(*this->mostSigOp->Copy());
        }
 
        if (this->leastSigOp) {
            generalized.SetLeastSigOp(*this->leastSigOp->Copy());
        }
 
        return std::make_unique<DerivedGeneralized>(generalized);
    }
 
    [[nodiscard]] auto Simplify() const -> std::unique_ptr<Expression> override
    {
        return Generalize()->Simplify();
    }
 
    [[nodiscard]] auto Integrate(const Expression& integrationVariable) const -> std::unique_ptr<Expression> override
    {
        return Generalize()->Integrate(integrationVariable);
    }
 
    [[nodiscard]] auto StructurallyEquivalent(const Expression& other) const -> bool final
    {
        if (this->GetType() != other.GetType()) {
            return false;
        }
 
        const std::unique_ptr<Expression> otherGeneralized = other.Generalize();
        const auto& otherBinaryGeneralized = static_cast<const DerivedGeneralized&>(*otherGeneralized);
 
        if (this->HasMostSigOp() == otherBinaryGeneralized.HasMostSigOp()) {
            if (this->HasMostSigOp() && otherBinaryGeneralized.HasMostSigOp()) {
                if (!mostSigOp->StructurallyEquivalent(otherBinaryGeneralized.GetMostSigOp())) {
                    return false;
                }
            }
        }
 
        if (this->HasLeastSigOp() == otherBinaryGeneralized.HasLeastSigOp()) {
            if (this->HasLeastSigOp() && otherBinaryGeneralized.HasLeastSigOp()) {
                if (!leastSigOp->StructurallyEquivalent(otherBinaryGeneralized.GetLeastSigOp())) {
                    return false;
                }
            }
        }
 
        return true;
    }
 
    auto Flatten(std::vector<std::unique_ptr<Expression>>& out) const -> void
    {
        if (mostSigOp) {
            if (this->mostSigOp->template Is<DerivedGeneralized>()) {
                auto generalizedMostSigOp = this->mostSigOp->Generalize();
                const auto& mostSigOp = static_cast<const DerivedGeneralized&>(*generalizedMostSigOp);
                mostSigOp.Flatten(out);
            } else {
                out.push_back(this->mostSigOp->Copy());
            }
        }
 
        if (leastSigOp) {
            if (this->leastSigOp->template Is<DerivedGeneralized>()) {
                auto generalizedLeastSigOp = this->leastSigOp->Generalize();
                const auto& leastSigOp = static_cast<const DerivedGeneralized&>(*generalizedLeastSigOp);
                leastSigOp.Flatten(out);
            } else {
                out.push_back(this->leastSigOp->Copy());
            }
        }
    }
 
    auto GetMostSigOp() const -> const MostSigOpT&
    {
        assert(mostSigOp != nullptr);
        return *mostSigOp;
    }
 
    auto GetLeastSigOp() const -> const LeastSigOpT&
    {
        assert(leastSigOp != nullptr);
        return *leastSigOp;
    }
 
    [[nodiscard]] auto HasMostSigOp() const -> bool
    {
        return mostSigOp != nullptr;
    }
 
    [[nodiscard]] auto HasLeastSigOp() const -> bool
    {
        return leastSigOp != nullptr;
    }
 
    template <typename T>
        requires IsAnyOf<T, MostSigOpT, Expression>
    auto SetMostSigOp(const T& op) -> bool
    {
        if constexpr (std::same_as<MostSigOpT, Expression>) {
            this->mostSigOp = op.Copy();
            return true;
        }
 
        if constexpr (std::same_as<MostSigOpT, T> && !std::same_as<MostSigOpT, Expression>) {
            this->mostSigOp = std::make_unique<MostSigOpT>(op);
            return true;
        }
 
        if (auto castedOp = Oasis::RecursiveCast<MostSigOpT>(op); castedOp) {
            mostSigOp = std::move(castedOp);
            return true;
        }
 
        return false;
    }
 
    template <typename T>
        requires IsAnyOf<T, LeastSigOpT, Expression>
    auto SetLeastSigOp(const T& op) -> bool
    {
        if constexpr (std::same_as<LeastSigOpT, Expression>) {
            this->leastSigOp = op.Copy();
            return true;
        }
 
        if constexpr (std::same_as<LeastSigOpT, T> && !std::same_as<LeastSigOpT, Expression>) {
            this->leastSigOp = std::make_unique<LeastSigOpT>(op);
            return true;
        }
 
        if (auto castedOp = Oasis::RecursiveCast<LeastSigOpT>(op); castedOp) {
            leastSigOp = std::move(castedOp);
            return true;
        }
 
        return false;
    }
 
    auto Substitute(const Expression& var, const Expression& val) -> std::unique_ptr<Expression> override
    {
        std::unique_ptr<Expression> left = ((GetMostSigOp()).Copy())->Substitute(var, val);
        std::unique_ptr<Expression> right = ((GetLeastSigOp().Copy())->Substitute(var, val));
        DerivedT<Expression, Expression> comb = DerivedT<Expression, Expression> { *left, *right };
        auto ret = comb.Simplify();
        return ret;
    }
    auto SwapOperands() const -> DerivedT<LeastSigOpT, MostSigOpT>
    {
        return DerivedT { *this->leastSigOp, *this->mostSigOp };
    }
 
    auto operator=(const BinaryExpression& other) -> BinaryExpression& = default;
 
    auto AcceptInternal(Visitor& visitor) const -> any override
    {
        const auto generalized = Generalize();
        const auto& derivedGeneralized = dynamic_cast<const DerivedGeneralized&>(*generalized);
        return visitor.Visit(derivedGeneralized);
    }
 
    std::unique_ptr<MostSigOpT> mostSigOp;
    std::unique_ptr<LeastSigOpT> leastSigOp;
};
 
} // Oasis
 
#endif // OASIS_BINARYEXPRESSION_HPP