code: function string(str) {
    assertString(str);
    var expected = "'" + str + "'";
    return Parsimmon(function(input, i) {
      var j = i + str.length;
      var head = input.slice(i, j);
      if (head === str) {
        return makeSuccess(j, head);
      } else {
        return makeFailure(i, expected);
      }
    });
  }
docs: -*- Constructors -*-