global lfsr_iterations  = 5;
global lfsr_length      = 4;
global lfsr_init_values = new bool[]{true, false, true, false};

bool xor(bool x, bool y) {
  return (x & !y) | (!x & y);
}

string string_of_bool(bool b) {
    if (b) { return "T"; }
    else   { return "F"; }
}

void print_lfsr(bool[] lfsr_register, int len) {
    for (var i = 0; i < len; i = i + 1;) {
        print_string(string_of_bool(lfsr_register[i]));
    }
    return;
}

int program(int argc, string[] argv) {
    /* Initialize the working register */
    var lfsr_register = new bool[lfsr_length];
    for (var i=0; i < lfsr_length; i=i+1;) {
      lfsr_register[i] = lfsr_init_values[i]; 
    }

    /* Do the computations */
    for (var i = 0; i < lfsr_iterations; i = i + 1;) {
        var new_first =
            xor(lfsr_register[lfsr_length - 1], lfsr_register[lfsr_length - 2]);
        for (var j = lfsr_length - 1; j > 0; j = j - 1;) {
            lfsr_register[j] = lfsr_register[j - 1];
        }
        lfsr_register[0] = new_first;
    }

    /* Print the initial and final bool arrays with a space separator */
    print_lfsr(lfsr_init_values, lfsr_length);
    print_string(" ");
    print_lfsr(lfsr_register, lfsr_length);

    return 0;
}