sclass SimpleLeftToRightParser > Meta {

  S text;

  LS tok;

  gettable TokPtr ptr;

  TokPtr mainLoopPtr;

  S currentToken;

  bool caseInsensitive;

  new L warnings;

  settable bool internIdentifiers;

  *() {}

  *(S *text) {}

  *(LS *tok) {}

  swappable LS tokenize(S text) { ret javaTok(text); }

  S t aka token() { ret currentToken; }

  S token(int i) { ret get(tok, ptr.idx()+i*2); }

  S next aka consume aka tpp() { var t = t(); next(1); ret t; }

  S lastSpace aka prevSpace() { ret get(tok, ptr.idx()-1); }

  S nextSpace() { ret get(tok, ptr.idx()+1); }

  S space(int i) { ret get(tok, ptr.idx()+i*2+1); }

  void unconsume() { next(-1); }

  bool tokEq aka eqTok(S a, S b) { ret eqOrEqic(caseInsensitive, a, b); }

  bool tokEqOneOf(S a, S... l) { ret any(l, b -> tokEq(a, b)); }

  bool is(int i, S t) { ret tokEq(token(i), t); }

  bool is(S t) { ret tokEq(currentToken, t); }

  bool is(S a, S... more) {

    if (!is(a)) false;

    for i over more:

      if (!is(i+1, more[i])) false;

    true;

  }

  bool was(S t) { ret tokEq(token(-1), t); }

  bool isOneOf(S... tokens) { ret tokEqOneOf(currentToken, tokens); }

  S[] consumeArray(int n) {

    S[] array = new[n];

    for i to n: array[i] = consume();

    ret array;

  }

  meta-for isInteger also as isIdentifier {

    bool isInteger() { ret isInteger(t()); }

    bool isInteger(S s) { ret main isInteger(s); }

  }

  S consumeIdentifier() {

    S s = assertIdentifier(consume());

    if (internIdentifiers)

      s = intern(s);

    ret s;

  }

  S consumeIdentifierOpt() { ret isIdentifier(t()) ? consumeIdentifier() : null; }

  int consumeInteger() { ret parseInt(assertInteger(consume())); }

  bool consumeOpt(S token) {

    if (!is(token)) false;

    consume();

    true;

  }

  void consume(S token) {

    if (!is(token))

      fail("Expected " + quote(token) + ", got " + describeToken(token());

    consume();

  }

  S describeToken(S token) {

    ret token == null ? "EOF" : quote(token);

  }

  S consumeOneOf(S... tokens) {

    if (!isOneOf(tokens))

      fail("Expected one of " + asList(tokens));

    ret consume();

  }

  void ptr(TokPtr ptr) { this.ptr = ptr; fetch(); }

  int idx aka tokIdx() { ret ptr.idx(); }

  int lTok() { ret l(tok); }

  int nRemainingTokens() { ret (lTok()-idx())/2; }

  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 = tokenize(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;

  }

  class AssureAdvance {

    TokPtr cur;

    { init(); }

    bool get() {

      if (atEnd()) false;

      if (eq(cur, ptr))

        fail("Parse loop didn't advance (current token: " + quote(token()) + ")");

      cur = ptr;

      true;

    }

  }

  void unknownToken {

    warn("Unknown token: " + t());

  }

  void warn(S msg) {

    warnings.add(print(msg));

  }

  // can also move backwards for negative n

  void next aka skip aka consume(int n) { 

    ptr(min(lTok(), 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);

  }

  LineAndColumn lineAndColumn(int idx) {

    ret tokenToLineAndColumn(ptr.plus(idx*2));

  }

  S consumeUntilSpaceOr(IF0<Bool> pred) {

    int i = idx();

    do next(); while (!atEnd() && empty(lastSpace()) && !pred!);

    ret joinSubList(tok, i, idx()-1);

  }

  void setText(S text) {

    this.text = text;

    tok = null;

    ptr = null;

  }

  int relativeIndexOf(S token) {

    int n = nRemainingTokens();

    for i to n:

      if (eqTok(token(i), token))

        ret i;

    ret -1;

  }

}