class LSystem {
  char [] alphabet = {
    'F', '+', '-', '[', ']'};
  String axiom;
  String [] rule = {
    "", "+", "-", "[", "]"};
  String tree;
  LSystem(String axiom, String ruleset){
    rule[0] = ruleset;
    this.axiom = axiom;
    tree = "";
  }
  void draw(float x, float y, float step, float angle){
    pushMatrix();
    translate(x,y);
    for(int i = 0; i < tree.length(); i++){
      switch(tree.charAt(i)){
        case 'F':
          line(0, 0, step, 0);
          translate(step, 0);
        break;
        case '+':
          rotate(angle);
        break;
        case '-':
          rotate(-angle);
        break;
        case '[':
          pushMatrix();
        break;
        case ']':
          popMatrix();
        break;
      }
    }
    popMatrix();
  }
  void iterate(int maxLength){
    tree = new String(axiom);
    int [] ruleLength = new int[alphabet.length];
    for (int i = 0; i < alphabet.length; i++){
      ruleLength[i] = rule[i].length();
    }
    for (int i = 0; i < maxLength; i++){
      int newLength = 0;
      for (int j = 0; j < tree.length(); j++){
        char c = tree.charAt(j);
        for (int k = 0; k < alphabet.length; k++){
          if (c == alphabet[k]){
            newLength += ruleLength[k];
            break;
          }
        }
      }
      StringBuffer newTree = new StringBuffer(newLength);
      for (int j = 0; j < tree.length(); j++){
        char c = tree.charAt(j);
        for (int k = 0; k < alphabet.length; k++){
          if (c == alphabet[k]){
            newTree.append(rule[k]);
            break;
          }
        }
      }
      tree = newTree.toString();
    }
  }
}