// file test.cpp //

TEST_CASE("Decrement operator moves the iterator backward", "[stage2]") {
    list l;
    append_to_list(l, { 5.55, 6.66, 7.77, 8.88 });

    auto it = l.end();
    SECTION("Prefix") {
        REQUIRE(*(--it) == 8.88);
        REQUIRE(*(--it) == 7.77);
        REQUIRE(*(--it) == 6.66);
        REQUIRE(*(--it) == 5.55);
        REQUIRE(it == l.begin());
    }

    SECTION("Postfix") {
        it--;
        REQUIRE(*(it--) == 8.88);
        REQUIRE(*(it--) == 7.77);
        REQUIRE(*(it--) == 6.66);
        REQUIRE(*it == 5.55);
        REQUIRE(it == l.begin());
    }
}

// list.hpp //

class list{
	...
	public:
		...

		class iterator{
			node* current_ptr = nullptr;
       		const list* o_list = nullptr;

			public:
				iterator(node* ptr, const list* gen);

                iterator& operator++();
                iterator operator++(int);
                iterator& operator--();
                iterator operator--(int);
		}
}


// file list.cpp // implementation of class iterator //

list::iterator::iterator(node *ptr, const list *gen) {
        this->current_ptr = ptr;
        this->o_list = gen;
    }

    list::iterator& list::iterator::operator++() {
        current_ptr = this->current_ptr->next;
        return *this;
    }

    list::iterator& list::iterator::operator--() {         // ??? Decrement operator moves the iterator backward, Prefix
        current_ptr = this->current_ptr->prev;
        return *this;
    }

    list::iterator list::iterator::operator++(int)
    {
        iterator old(*this);
        ++(*this);
        return old;
    }

    list::iterator list::iterator::operator--(int)
    {
        iterator left(*this);
        --(*this);
        return left;
    }