12.02.cpp

/*
 * Exercise 12.2: Write your own version of the StrBlob class including the
 * const versions of front and back.
 *
 * By Faisal Saadatmand
 */

#include <exception>
#include <iostream>
#include <memory>
#include <string>
#include <vector>

class StrBlob {
	public:
		using size_type = std::vector<std::string>::size_type;
		StrBlob();
		StrBlob(std::initializer_list<std::string> il);
		size_type size() const { return data->size(); }
		bool empty() const { return data->empty(); }
		// add and remove elements
		void push_back(const std::string &t) { data->push_back(t); }
		void pop_back();
		// element access
		std::string& front();
		std::string& back();
		std::string& front() const;
		std::string& back() const;
	private:
		std::shared_ptr<std::vector<std::string>> data;
		// throws msg if data[i] isn't valid
		void check(size_type i, const std::string &msg) const;
};

// constructors
StrBlob::StrBlob() : data(std::make_shared<std::vector<std::string>>()) {}
StrBlob::StrBlob(std::initializer_list<std::string> il) :
	data(std::make_shared<std::vector<std::string>>(il)) {}

void StrBlob::check(size_t i, const std::string &msg) const
{
	if (i >= data->size())
		throw std::out_of_range(msg);
}

void StrBlob::pop_back()
{
	check(0, "back on empty StrBlob");
	data->pop_back();
}

std::string& StrBlob::front()
{
	check(0, "front on empty StrBlob");
	return data->front();
}

std::string& StrBlob::front() const
{
	check(0, "front on empty StrBlob");
	return data->front();
}

std::string& StrBlob::back()
{
	check(0, "back on empty StrBlob");
	return data->back();
}

std::string& StrBlob::back() const
{
	check(0, "back on empty StrBlob");
	return data->back();
}

int main()
{
	const StrBlob s({"tree", "cat", "fall"});
	std::cout << s.front() << ' ' << s.back() << ' ' << s.size() <<  '\n';

	StrBlob s2;
	s2.push_back("tall");
	s2.push_back("ball");
	s2.push_back("wall");
	std::cout << s2.front() << ' ' << s2.back() << ' ' << s2.size() <<  '\n';

	return 0;
}