sparse_vector_base.hh

#ifndef SPARSE_VECTOR_BASE_HH
#define SPARSE_VECTOR_BASE_HH
 
#ifdef HAVE_CONFIG_H
#include <config.h>
#endif
 
#include <iosfwd>
#include <unordered_map>
 
#include "aux.hh"
 
namespace LocARNA {
 
    template <typename Derived,typename ValueType, typename KeyType=size_t>
    class SparseVectorBase {
    public:
        using derived_type = Derived;
        using value_type = ValueType; 
        using key_type = KeyType; 
        using map_type = std::unordered_map<KeyType, ValueType>;
 
        using size_type = size_t; 
 
        using const_iterator = typename map_type::const_iterator;
 
        using iterator = typename map_type::iterator;
 
        class element_proxy {
        public:
            element_proxy(derived_type *v, key_type k) : v_(v), k_(k) {}
 
            operator value_type() {
                typename map_type::const_iterator it = v_->the_map_.find(k_);
                if (it == v_->the_map_.end())
                    return v_->def_;
                else
                    return it->second;
            }
 
            element_proxy
            operator+=(const value_type &x) {
                const_iterator it = v_->the_map_.find(k_);
                if (it == v_->the_map_.end())
                    v_->the_map_[k_] = v_->def_ + x;
                else
                    v_->the_map_[k_] += x;
 
                return *this;
            }
 
            element_proxy &
            operator=(const value_type &x) {
                if (x == v_->def_) {
                    v_->the_map_.erase(k_);
                } else {
                    // the following replaces v_->the_map_[k_] = x;
                    // but never calls the default constructor for value_type
 
                    typename map_type::iterator it = v_->the_map_.find(k_);
                    if (it != v_->the_map_.end()) {
                        it->second = x;
                    } else {
                        v_->the_map_.insert(typename map_type::value_type(k_, x));
                    }
                }
                return *this;
            }
 
        private:
            derived_type *v_;
            key_type k_;
        }; //end class element_proxy
 
 
        explicit SparseVectorBase(const value_type def) : def_(def) {}
 
        element_proxy operator[](const key_type &i) {
            return element_proxy( static_cast<derived_type*>(this), i );
        }
 
        const value_type &operator[](const key_type &i) const {
            const_iterator it = the_map_.find(key_type(i));
            if (it == the_map_.end())
                return def_;
            else
                return it->second;
        }
 
        void
        set(const key_type &i, const value_type &val) {
            typename map_type::iterator it = the_map_.find(key_type(i));
            if (it != the_map_.end()) {
                it->second = val;
            } else {
                the_map_.insert(typename map_type::value_type(key_type(i), val));
            }
        }
 
        value_type &
        ref(const key_type &i) {
            auto it = the_map_.find(i);
            if (it == the_map_.end()) {
                the_map_[i] = def_;
                it = the_map_.find(i);
            }
            return it->second;
        }
 
        void
        reset(const key_type &i) {
            typename map_type::iterator it = the_map_.find(key_type(i));
            if (it != the_map_.end()) {
                the_map_.erase(key_type(i));
            }
        }
 
        size_type
        size() const {
            return the_map_.size();
        }
 
        bool
        empty() const {
            return the_map_.empty();
        }
 
        void
        clear() {
            the_map_.clear();
        }
 
        const_iterator
        begin() const {
            return the_map_.begin();
        }
 
        const_iterator
        end() const {
            return the_map_.end();
        }
 
        const value_type &
        def() const {
            return def_;
        }
 
    protected:
        value_type def_;   
        map_type the_map_; 
    };
 
} // end namespace LocARNA
 
#endif // SPARSE_VECTOR_HH