sclass SimpleLeftToRightParser {
  settable S text;
  LS tok;
  ListAndIndex<S> ptr, mainLoopPtr;
  S currentToken;
  bool caseInsensitive;
  new L warnings;
  
  *() {}
  *(S *text) {}
  *(LS *tok) {}
  
  S t aka token() { ret currentToken; }
  S token(int i) { ret get(tok, ptr.idx()+i*2); }
  S tpp() { var t = t(); next(); ret t; }
  S lastSpace() { ret get(tok, ptr.idx()-1); }
  
  bool is(S t) { ret eqOrEqic(caseInsensitive, currentToken, t); }
  bool was(S t) { ret eqOrEqic(caseInsensitive, token(-1), t); }
  
  meta-for isInteger also as isIdentifier {
    bool isInteger() { ret isInteger(t()); }
    bool isInteger(S s) { ret main isInteger(s); }
  }
  
  void next { if (!endOfText()) ptr(ptr.plus(2)); }
  
  void ptr(ListAndIndex<S> ptr) { this.ptr = ptr; fetch(); }
  int idx() { ret ptr.idx(); }

  bool atEnd aka endOfText() { ret ptr.atEnd(); }
    
  void fetch { currentToken = ptr!; }
  
  bool lineBreak() { ret containsLineBreak(get(tok, ptr.idx()-1)); }
  bool atEndOrLineBreak() { ret atEnd() || lineBreak(); }
  
  void init {
    tok if null = javaTok(text);
    if (ptr == null) ptr(ListAndIndex(tok, 1));
  }
  
  bool mainLoop() {
    init();
    if (atEnd()) false;
    if (eq(mainLoopPtr, ptr))
      fail("main loop didn't advance (current token: " + quote(token()) + ")");
    mainLoopPtr = ptr;
    true;
  }
  
  void unknownToken {
    warn("Unknown token: " + t());
  }
  
  void warn(S msg) {
    warnings.add(print(msg));
  }
  
  void next(int n) { 
    ptr(ptr.idx()+n*2);
  }
  
  // if i points to an N token, it is incremented
  void ptr(int i) {
    ptr(ListAndIndex(tok, min(i | 1, l(tok))));
  }
  
  LineAndColumn lineAndColumn() {
    ret tokenToLineAndColumn(ptr);
  }
}