/*

	braindrain.d

	purpose: Brainfuck'a'like outputgenerator

	It isn't like the original brainfuck, because the implementation of ','
	for getting a char from stdin isn't there...

	compile with dmd braindrain.d
	testet with dmd v1.014 on WinXP

	Usageexample:
	$ braindrain "++++++++++[>+++++++>++++++++++>+++>+<<<<-]>++.>+.+++++++..+++."

	It should print "Hello" then.

	Possible improvements, if I have sparetime: none, 'cause my brain hurts now.

	If you want to improve this: Try to add the ',' from bf and the possiblility to load
	files to have fun, instead of using a command line parameter.

	Have fun, Gregor Kopp (gekkonier)
*/


import std.stdio;

class Stack(T)
{
    private T[] data;
    private T lastone;
    public void push(T element)
    {
        data.length = this.size + 1;
        data[this.size - 1] = element;
    }
    public T pop()
    {
        if (this.size > 0)
        {
            lastone = this.last;
            data.length = this.size - 1;
            return lastone;
        }
        else assert(0);
    }
    public int size()
    {
        return data.length;
    }
    public T last()
    {
    	return data[this.size - 1];
    }
}


int main(char[][] args)
{
    char[300_000] cells;
    for ( int i = 0; i < 300_000; i++ ) { cells[i] += 1; }
    int position, kommandoindex = 0;
    Stack!(char) klammernstack = new Stack!(char);
    char[] kommandos;

	try
	{
		kommandos = args[1];
	}
	catch
	{
		writefln("No Args? Try this out:");
		writefln("braindrain \"++++++++++[>+++++++>++++++++++>+++>+<<<<-]>++.>+.+++++++..+++.\"");
		writefln("It should print 'Hello'");
	}

    while (kommandoindex < kommandos.length)
    {
        switch (kommandos[kommandoindex])
        {
        case '>':
            position += 1;
            break;
        case '<':
            position -= 1;
            break;
        case '+':
            cells[position] += 1;
            break;
        case '-':
            cells[position] -= 1;
            break;
        case '.':
			writef(cells[position]);
			break;
        case '[':
            klammernstack.push(kommandoindex);
            if (cells[position] == 0)
            {
                while (kommandos[kommandoindex] != '?')
                {
                    kommandoindex += 1;
                }
            }
            break;
        case ']':
            if (cells[position] != 0)
            {
                kommandoindex = klammernstack.last;
            }
            else
            {
                klammernstack.pop;
            }
            break;
        }
        kommandoindex += 1;
    }
    return 0;
}