brain.hpp

// Copyright plasma_effect 2014.
// Distributed under the Boost Software License, Version 1.0.
//(See accompanying file LICENSE_1_0.txt or copy at
//	http://www.boost.org/LICENSE_1_0.txt)
#pragma once

#include<stdexcept>
#include<stack>

namespace plasma_brain
{
	template<class InputIterator,class BidirectionalIterator,class InputStream,class OutputStream>
	void brein_f(
		InputIterator code_begin,
		InputIterator code_end,
		BidirectionalIterator memory_begin,
		BidirectionalIterator memory_end,
		InputStream& input_stream,
		OutputStream& output_stream)
	{
		auto memory_ite = memory_begin;
		std::stack<InputIterator> loop_stack;

		for (auto code_ite = code_begin; code_ite != code_end; ++code_ite)
		{
			if (*code_ite == '>')
			{
				++memory_ite;
				if (memory_ite == memory_end)
					throw std::out_of_range(R"(brainf**k exception: ">" memory iterator cant point to end of memories)");
			}
			else if (*code_ite == '<')
			{
				if (memory_ite == memory_begin)
					throw std::out_of_range(R"(brainf**k exception: "<" memory iterator cant point to back of begin of memories)");
				--memory_ite;
			}
			else if (*code_ite == '+')
			{
				++(*memory_ite);
			}
			else if (*code_ite == '-')
			{
				--(*memory_ite);
			}
			else if (*code_ite == '.')
			{
				output_stream << (*memory_ite);
			}
			else if (*code_ite == ',')
			{
				input_stream >> (*memory_ite);
			}
			else if (*code_ite == '[')
			{
				if (*code_ite == '\0')
				{
					int N = 1;
					while (N != 0)
					{
						++code_ite;
						if (code_ite == code_end)
							throw std::out_of_range(R"(brainf**k exception: "[" dont find "]")");
						if (*code_ite == '[')
						{
							++N;
						}
						else if (*code_ite == ']')
						{
							--N;
						}
					}
				}
				else
				{
					loop_stack.push(code_ite);
				}
			}
			else if (*code_ite == ']')
			{
				if (loop_stack.empty())
					throw std::out_of_range(R"(brainf**k exception: "]" dont find "[")");
				auto next_iterator = loop_stack.top();
				loop_stack.pop();
				if (*memory_ite != '\0')
				{
					code_ite = next_iterator;
					loop_stack.push(next_iterator);
				}
			}
		}
	}
}