#ifndef MY_LEXER
#define MY_LEXER

#include <iostream>
#include <sstream>
#include <string>
#include "MathHelpFunctions.h"

class Lexer
{
private:
	std::istream reader;
	std::string current;
public:
	Lexer(const std::istream &reader) : reader(reader)
	{
		Read();
	}

	void Reader(std::istream &value)
	{
		reader = value;
		Read();
	}

	std::istream &Reader()
	{
		return reader;
	}

	std::string Read()
	{
		char now = 0;

		if (reader.eof())
			return "/n/r";
		now = reader.peek();

		while (now == ' ')
		{
			reader >> now;
			now = reader.peek();
		}

		std::string rv = current;
		switch (now)
		{
		case '+':
			reader >> now;
			current = now;
			break;
		case '-':
			reader >> now;
			current = now;
			break;
		case '*':
			reader >> now;
			current = now;
			break;
		default:
			current = "";
			while (IsNumber(now))
			{
				reader >> now;
				current += now;
				now = reader.peek();
			}
			if (current.length() == 0)
				throw "Parse failed: incorrect input string.";
		}
		return rv;

	}

	std::string Peek()
	{
		return current;
	}
};

#endif