import java.io.BufferedReader;
import java.io.FileNotFoundException;
import java.io.FileReader;
import java.io.IOException;
import java.io.PrintWriter;
import java.util.Arrays;
import java.util.Stack;


public class Implementation implements Calculator {

	String [] list = new  String [1000] ;
	int size = 0 ;
	int index = -1 ;

	@Override
	public void Input(String s) {
		// TODO Auto-generated method stub
		index++;
		list[index] = s ;
		size++;

	}

	@Override
	public String current_formula() {
		// TODO Auto-generated method stub

		String up = END_LIST_UP ;
		String down = END_LIST_DOWN ;
		if (index < 0) return up;
		if (index >= size) return down;
		return list[index];
	}

	@Override
	 public String getResults() {
		// TODO Auto-generated method stub

		int r = list[index].length();
		String not  = BAD_FORMAT ;
		for(int i=1 ;i<r ;i++)
		{
			 char b =list[index].charAt(i) ;
			 char c =list[index].charAt(i-1) ;
			 if(b== '-' || b=='+' || b=='*' || b=='/')
			 {
				 if(i==r-1) return not ;
				 else if(c!= '-' && c!='+' && c!='*' && c!='/') continue ;
				 else
				 {
					 if(b =='-' && (c=='*' || c=='/')) continue ;
					 else return not ;
				 }
			 }
		}
		String no = DIVISION_BY_ZERO ;
		GetResults answer = new GetResults (list[index]) ;
		if (answer.flag == 1 ) return no ;
		String d = Double.toString(answer.l);
		return d;
	}

	@Override
	public void save() throws Exception {
		// TODO Auto-generated method stub

		PrintWriter is = new PrintWriter("Compute.out");
        for (int i=size-1 ; i>=size-5 ; i--)
        {
        		if(i<0) break ;
                is.println(list[i]);
        }
        is.close();
	}

	@Override
	public void load() throws Exception {
		// TODO Auto-generated method stub

		Arrays.fill(list, null);
        BufferedReader sc = new BufferedReader(new FileReader("Compute.out"));
        String enter;
        int g = -1;
        int mass = 0;
        while ( (enter = sc.readLine()) != null)
        {
        	g++;
    		list[g] = enter ;
    		mass++;

        }
        size= mass ;
        index = g;
        sc.close();

	}

	@Override
	public String prev() {
		// TODO Auto-generated method stub

		index-- ;
		String ret = current_formula() ;
		if(index < 0) index++ ;
		return ret ;
	}

	@Override
	public String next() {
		// TODO Auto-generated method stub

		index++ ;
		String ret = current_formula() ;
		if(index >=  size ) index-- ;
		return ret ;
	}

}