Factors.hpp

#ifndef _FACTORS_HPP_
#define _FACTORS_HPP_

#include <iostream>
#include <utility>
#include "../Ring/BPASRing.hpp"
#include "../ExpressionTree/ExpressionTree.hpp"
#include "../Utils/TemplateHelpers.hpp"

/**
 * A Factor is a pair of a BPASRing element and an integer exponent.
 * Template Ring should derive from BPASRing.
 */
template <class Ring>
class Factor : public std::pair<Ring, int>, public ExpressionTreeConvert, private Derived_from<Ring, BPASRing<Ring>> {

public:
    /**
     * Construct an empty factor.
     */
    Factor() : std::pair<Ring,int>() {}

    /**
     * Construct a factor from a Ring element and an exponent.
     * @param r the Ring element
     * @param e the exponent
     */
    Factor(const Ring& r, int e) : std::pair<Ring,int>(r,e) {}

    /**
     * Move-construct a factor from a Ring element and an exponent.
     * @param r the Ring element
     * @param e the exponent
     */
    Factor(Ring&& r, int e) : std::pair<Ring,int>(r,e) {}

    /**
     * Construct a Factor from a std::pair of a Ring element and integer exponent.
     * @param p the pair
     */
    Factor(const std::pair<Ring, int>& p) : std::pair<Ring, int>(p) {}

    /** 
     * Equality comparison operator.
     * @param f the Factor to compare
     * @return true iff *this == f.
     */
    bool operator==(const Factor<Ring>& f) {
        return (this->first == f.first && this->second == f.second);
    }

    /** 
     * Inequality comparison operator.
     * @param f the Factor to compare
     * @return true iff *this != f.
     */
    bool operator!=(const Factor<Ring>& f) {
        return (this->first != f.first || this->second != f.second);
    }

    /**
     * Output operator, defines a to string conversion. 
     * @param out the output stream
     * @param f the Factor
     */
    friend std::ostream& operator<<(std::ostream& out, const Factor<Ring>& f) {
        out << "[" << f.first << ", " << f.second << "]";
        return out;

    }

    /**
     * Convert the Factor to an ExpressionTree.
     * @return the ExpressionTree
     */
    ExpressionTree convertToExpressionTree() const {
        std::vector<ExpressionTree> trees;
        trees.push_back(this->first.convertToExpressionTree());
        trees.emplace_back(new ExprTreeNode(this->second));

        return ExpressionTree(trees);
    }
};

/**
 * A simple data structure for encapsulating a collection of Factor elements.
 * Factors are encoded as a list of Factor items. That is, a pair of a Ring 
 * element and an integer representing its exponent. This list of Factor elements
 * is augmented by an invertible element of the ring (if one such exists) as a constant
 * multiplicative factor.  
 */
template <class Ring>
class Factors : public ExpressionTreeConvert, private Derived_from<Ring, BPASRing<Ring>> {
    
private: 
    Ring u;
    std::vector<Factor<Ring>> facts;

public:
    
    /**
     * Default constructor. Constructs an empty list of factors.
     */
    Factors();

    /**
     * Construct a Factors with a single factor. 
     * @param r the Ring element
     */
    Factors(const Ring& r);

    /**
     * Create a Factors from a list of Ring elements. Each factor is assumed
     * to have an exponent of 1. 
     * @param v the vector of Ring elements.
     */
    Factors(const std::vector<Ring>& v);
    
    /**
     * Create a Factors from a list of Ring elements and a parallel array of integers
     * as exponents for each ring element.
     * @param v the vector of Ring elements
     * @param e the parallel vector of integer exponents
     */
    Factors(const std::vector<Ring>& v, const std::vector<int>& e);

    /**
     * Create a Factors from a list of ring elements, a parallel array of integers
     * as exponents for each ring element, and a ring element representing the
     * invertible unit of the Ring. 
     * @param v the vector of Ring elements
     * @param e the parallel vector of integer exponents
     * @param u the multicative factor
     */
    Factors(const std::vector<Ring>& v, const std::vector<int>& e, const Ring& u);

    /**
     * Create a Factors from a vector of Factor elements.
     * @param v the vector of Factor elements.
     */
    Factors(const std::vector<Factor<Ring>>& v);

    /**
     * Create a Factors from a vector of Factor elements and an invertible Ring element.
     * @param v the vector of Factor elements.
     * @param u the invertible Ring element.
     */
    Factors(const std::vector<Factor<Ring>>& v, const Ring& u);

    /**
     * Copy consturctor.
     * @param f the Factors to copy.
     */
    Factors(const Factors& f);
    
    /**
     * Move consturctor.
     * @param f the Factors to move.
     */
    Factors(Factors&& f);

    /**
     * Destructor.
     */
    ~Factors();

    /**
     * Set the invertible Ring element.
     * @param r the new invertible Ring element.
     */
    inline void setRingElement(const Ring& r) {
        u = r;
    }

    /**
     * Get the invertible Ring element.
     * @return the invertible Ring element of this Factors
     */
    inline Ring ringElement() const {
        return u;
    }

    /**
     * Multiply this Factors invertible Ring element by another Ring element.
     * @param r the other Ring element.
     */
    inline void multiplyRingElement(const Ring& r) {
        u *= r;
    }

    /**
     * Get the list of Factor elements.
     * @return the vector of Factor elements.
     */
    inline std::vector<Factor<Ring>> factors() const {
        return facts;
    }
    
    /**
     * Get the i'th Factor.
     * @param i the index
     * @return the Factor at index i
     */
    inline Factor<Ring> factor(int i) const {
        if (i < facts.size())
            return facts[i];
        else {
            std::cerr << "BPAS: error, i exceeds array bounds of list of factors" << std::endl;
            exit(1);
        }
    }

    /**
     * Set the list of Factor elements.
     * @param v the vector of Factor elements.
     */
    inline void setFactors(const std::vector<Factor<Ring>>& v) {
        facts = v;
    }

    /**
     * A Factor to the list of Factor elements.
     * @param f the Factor to add.
     */
    inline void addFactor(const Factor<Ring>& f) {
        if (f.first.isOne()) {
            return;
        }
        for (int i = 0; i < facts.size(); ++i) {
            if (f.first == facts[i].first) {
                facts[i].second += f.second;
                return;
            }
        }
        facts.push_back(f);
    }

    /**
     * Add a Ring element and its corresponding exponent as a Factor.
     * @param r the ring element.
     * @param e the exponent
     */
    inline void addFactor(const Ring& r, int e) {
        if (r.isOne()) {
            return;
        }
        for (int i = 0; i < facts.size(); ++i) {
            if (r == facts[i].first) {
                facts[i].second += e;
                return;
            }
        }
        facts.emplace_back(r, e);
    }


    /**
     * Add a Ring element and its corresponding exponent as a Factor.
     * @param r the ring element.
     * @param e the exponent
     */
    inline void addFactor(Ring&& r, int e) {
        if (r.isOne()) {
            return;
        }
        for (int i = 0; i < facts.size(); ++i) {
            if (r == facts[i].first) {
                facts[i].second += e;
                return;
            }
        }
        facts.emplace_back(r, e);
    }

    /**
     * Combine another Factors' list of Factor elements with this Factors. This does
     * not modify the invertible ring element.
     * @param f the Factors object
     */
    inline void addFactors(const Factors<Ring> f) {
        for (int i = 0; i < f.facts.size(); ++i) {
            this->addFactor(f.facts[i]);
        }
    }

    /**
     * Get the number of Factor elements in this Factors object.
     * @return the number of Factor elements.
     */
    inline size_t size() const {
        return facts.size();
    }

    /**
     * Copy assignment.
     * @param f the Factors to copy from.
     */
    Factors<Ring>& operator=(const Factors<Ring>& f);
    
    /**
     * Move assignment.
     * @param f the Factors to move from.
     */
    Factors<Ring>& operator=(Factors<Ring>&& f);

    /**
     * Equality testing for Factors. Does NOT check if, when factors are distributed,
     * that the underlying elements are the same. Only if the factoirzation is the same.
     * @param f the Factors to test equality with.
     * @return true iff all factors are equal in both Factors.
     */
    bool operator==(const Factors<Ring>& f) const;

    /**
     * Inequality testing for Factors. Does NOT check if, when factors are distributed,
     * that the underlying elements are the same. Only if the factoirzation is the same.
     * @param f the Factors to test equality with.
     * @return false iff all factors are equal in both Factors.
     */
    inline bool operator!=(const Factors<Ring>& f) const {
        return !(*this == f);
    }

    /**
     * Indexing operator.
     * @param idx the index 
     * @return the Factor at index idx.
     */
    inline Factor<Ring>& operator[](size_t idx) {
        return facts[idx];
    }

    /**
     * Output operator. Defines a to string conversion. 
     * @param out the output stream
     * @param f the Factors to output
     */
    friend std::ostream& operator<<(std::ostream& out, const Factors<Ring>& f) {
        out << "[" << f.u << ", [";


        for (int i = 0; i < f.facts.size(); ++i) {
            out << f.facts[i];
            if (i + 1 < f.facts.size()) {
                out << ", ";
            }
        }

        out << "]]";
        return out;
    }

    /**
     * Convert the Factors object to an ExpressionTree.
     * @return the ExpressionTree encoding the Factors.
     */ 
    ExpressionTree convertToExpressionTree() const {
        std::vector<ExpressionTree> trees;
        ExpressionTree t;
        t.fromVector(facts);

        trees.push_back(u.convertToExpressionTree());
        trees.push_back(t);

        return ExpressionTree(trees);
    }

};  


//Include the implementation
#include "Factors_impl.hxx"

#endif