@{
    println(x) { print(x, "\n"); }

    treeCopy(x) {
      l = {};
      k = _keys(x);
      if (k == null) {
        return clone(x);
      } else {
        for (i in k) {
          l[k[i]] = clone(treeCopy(x[k[i]]));
        }
        return clone(l);
      }
    }

    getId(x) { { identifier: x, __proto__: C_id }; }

    getEnum(x) { { attributeL: null, expression: null, name: getId(x), __proto__: C_enum }; }

    getComma() { { text: ",", comment: { text : " ", __proto__: Comment }, __proto__: Token }; }
    
    getComment(x) { { text : x, __proto__: Comment }; }

    // adding the element e at the end of the list l
    append(s, e) {
      s[length(s)] = e;
    }

    // If g then we add a filter on the application of the function f to each element of seq
    map(f, seq, g) {
      out = {};
      if (g) {
        for (i in seq) {
          e = seq[i];
          if (g(e)) { e = f(e); }
          append(out, e);
        }
      } else {
        for (i in seq) {
          append(out, f(seq[i]));
        }
      }
      out;
    }

    notToken(x)     { x.__proto__ != Token  }

    // Select element e of s if the the result of the application of f on e is true
    select(f, s) {
      out = {};
      for (i in s) {
        e = s[i];
        if (f(e)) { append(out, e); }
      }
      out;
    }

    // Select element e of s if the the result of the application of f on e is false
    reject(f, s) {
      out = {};
      for (i in s) {
        e = s[i];
        if (!f(e)) { append(out, e); }
      }
      out;
    }
    
    // Get the last element of s
    last(s) {
      s[length(s)-1];
    }
    
    nil;
}