Revert "PEG Parser: under review at http://codereview.chromium.org/8399029"

utils/peg/pegparser.dart

-// Copyright (c) 2011, the Dart project authors.  Please see the AUTHORS file
-// for details. All rights reserved. Use of this source code is governed by a
-// BSD-style license that can be found in the LICENSE file.
-
-#library('Peg Parser');
-
-/*
- * The following functions are combinators for building Rules.
- *
- * A rule is one of the following
- * - A String which matches the string literally.
- * - A Symbol which matches the symbol's definition.
- * - A list of rules with an optional reducing function, which matches a sequence.
- * - The result of calling one of the combinators.
- *
- * Some rules are 'value-generating' rules, they return an 'abstract syntax
- * tree' with the match.  If a rule is not value-generating [:null:] is the
- * value.
- *
- * A Symbol is always a value-generating rule. If the value is not required, use
- * [:SKIP(aSymbol):] in place of [:aSymbol:].
- *
- * A String is not a value-generating rule but can be converted into one by
- * using [:TEXT('string'):] in place of [:'string':].
- *
- * A list or sequence is value-generating depending on the subrules.  The
- * sequence is value-generating if any of the subrules are value-generating or
- * if there is a reducing function.  If no reducing function is given, the value
- * returned depends on the number of value-generating subrules.  If there is
- * only one value generating subrule, that provideds the value for the sequence.
- * If there are more, then the value is a list of the values of the
- * value-generating subrules.
- */
-
-/**
- * Matches one character by a predicate on the character code.
- * If [spec] is an int, that character is matched.
- * If [spec] is a function it is used
- *
- * Example [: CHARCODE((code) => 48 <= code && code <= 57) :] recognizes an
- * ASCII digit.
- *
- * CHARCODE does not generate a value.
- */
-_Rule CHARCODE(spec, [name]) {
-  if (spec is int)
-    return new _CharCodeRule((code) => code == spec, name);
-  else
-    return new _CharCodeRule(spec, name);
-}
-
-/**
- * Matches one of the [characters].
- *
- * CHAR does not generate a value.
- */
-_Rule CHAR([characters]) {
-  if (characters == null)
-    return const _AnyCharRule();
-  if (characters is int)
-    return CHARCODE(characters);
-
-  // Find the range of character codes and construct an array of flags for codes
-  // within the range.
-  List<int> codes = characters.charCodes();
-  codes.sort((a, b) => a < b ? -1 : a > b ? 1 : 0);
-  int lo = codes[0];
-  int hi = codes[codes.length - 1];
-  if (lo == hi)
-    return CHARCODE(lo);
-  int len = hi - lo + 1;
-  var flags = new List<bool>(len);
-  for (int i = 0; i < len; ++i)
-    flags[i] = false;
-  for (int code in codes)
-    flags[code - lo] = true;
-
-  return CHARCODE((code) => code >= lo && code <= hi && flags[code - lo]);
-}
-
-/**
- * Matches the end of the input.
- *
- * END does not generate a value.
- */
-_Rule get END() => new _EndOfInputRule();
-
-/**
- * Throws an exception.
- */
-_Rule ERROR(String message) => new _ErrorRule(message);
-
-/**
- * Matches [rule] but does not consume the input.  Useful for matching a right
- * context.
- *
- * AT does not generate a value.
- */
-_Rule AT(rule) => new _ContextRule(_compile(rule));
-
-/**
- * Matches when [rule] does not match.  No input is consumed.
- *
- * NOT does not generate a value.
- */
-_Rule NOT(rule) => new _NegativeContextRule(_compile(rule));
-
-/**
- * Matches [rule] but generates no value even if [rule] generates a value.
- *
- * SKIP never generates a value.
- */
-_Rule SKIP(rule) => new _SkipRule(_compile(rule));
-
-/**
- * Matches [rule] in a lexical context where whitespace is not automatically
- * skipped.  Useful for matching what would normally be considered to be tokens.
- * [name] is a user-friendly description of what is being matched and is used in
- * error messages.
- *
- * LEX(rule)
- * LEX(name, rule)
- *
- * LEX does not generate a value.  If a value is required, wrap LEX with TEXT.
- */
-_Rule LEX(arg1, [arg2]) {
-  if (arg2 == null)
-    return new _LexicalRule(arg1 is String ? arg1 : null, _compile(arg1));
-  else
-    return new _LexicalRule(arg1, _compile(arg2));
-}
-
-/**
- * Matches [rule] and generates a value from the matched text. If the [rule]
- * matches, then TEXT(rule) matches and has a value derived from the string
- * fragment that was matched.  The default derived value is the string fragment.
- *
- * TEXT always generates a value.
- */
-_Rule TEXT(rule, [extractor]) =>
-  new _TextValueRule(_compile(rule),
-                     extractor == null
-                     ? (string, start, end) => string.substring(start, end)
-                     : extractor);
-
-/**
- * Matches an optional rule.
- *
- * MAYBE is a value generating matcher.
- *
- * If [rule] is value generating then the value is the value generated by [rule]
- * if it matches, and [:null:] if it does not.
- *
- * If [rule] is not value generatinge then the value is [:true:] if [rule]
- * matches and [:false:] if it does not.
- */
-_Rule MAYBE(rule) => new _OptionalRule(_compile(rule));
-
-/**
- * MANY(rule) matches [rule] [min] or more times.
- * [min] must be 0 or 1.
- * If [separator] is provided it is used to match a separator between matches of
- * [rule].
- *
- * MANY is a value generating matcher.  The value is a list of the matches of
- * [rule].  The list may be empty if [:min == 0:].
- */
-_Rule MANY(rule, [separator = null, int min = 1]) {
-  assert(0 <= min && min <= 1);
-  return new _RepeatRule(_compile(rule), _compileOptional(separator), min);
-}
-
-/**
- * Matches [rule] zero or more times.  Shorthand for [:MANY(rule, min:0):]
- * TODO: retire min: parameter?
- *
- * MANY0 is a value generating matcher.
- */
-_Rule MANY0(rule, [separator = null]) {
-  return new _RepeatRule(_compile(rule), _compileOptional(separator), 0);
-}
-
-/**
- * Matches [rules] in order until one succeeds.
- *
- * OR is value-generating.
- */
-_Rule OR([a,b,c,d,e,f,g,h,i,j,k,l,m,n,o,p,q,r,s,t,u,v,w,x,y,z]) =>
-    _compileMultiRule(
-        (a is List && b == null)  // Backward compat. OR([a, b]) => OR(a, b).
-          ? a
-          : _unspread(a,b,c,d,e,f,g,h,i,j,k,l,m,n,o,p,q,r,s,t,u,v,w,x,y,z),
-        false,
-        (compiledRules, valueCount, reducer) =>
-            new _ChoiceRule(compiledRules));
-
-
-
-_Rule SEQ([a,b,c,d,e,f,g,h,i,j,k,l,m,n,o,p,q,r,s,t,u,v,w,x,y,z]) =>
-  _compile(_unspread(a,b,c,d,e,f,g,h,i,j,k,l,m,n,o,p,q,r,s,t,u,v,w,x,y,z));
-
-/**
- * Matches [rule]
- */
-_Rule MEMO(rule) => new _MemoRule(_compile(rule));
-
-_Rule TAG(tag, rule) => _compile([rule, (ast) => [tag, ast]]);
-
-
-class ParseError implements Exception {
-  const ParseError(String this._message);
-  String toString() => _message;
-  final String _message;
-}
-
-/**
- * A grammar is a collection of symbols and rules that may be used to parse an
- * input.
- */
-class Grammar {
-  Map<String, Symbol> _symbols;
-
-  /** This rule may be set by the user to define whitespace. */
-  _Rule _whitespace;
-
-  _Rule get whitespace() => _whitespace;
-  void set whitespace(rule) { _whitespace = _compile(rule); }
-
-  Grammar() {
-    _symbols = new Map<String, Symbol>();
-    whitespace = CHAR(' \t\r\n');
-  }
-
-  /**
-   * operator [] is used to find or create symbols. Symbols may appear in rules
-   * to define recursive rules.
-   */
-  Symbol operator [](String name) {
-    if (_symbols.containsKey(name))
-      return _symbols[name];
-    Symbol s = new Symbol(name, this);
-    _symbols[name] = s;
-    return s;
-  }
-
-  /**
-   * Parses the input string and returns the parsed AST, or throws an exception
-   * if the input can't be parsed.
-   */
-  parse(root, String text) {
-    for (var symbol in _symbols.getValues())
-      if (symbol._rule == null)
-        print('${symbol.name} is undefined');
-
-    var state = new _ParserState(text, whitespace: whitespace);
-    var match = _compile(root).match(state, 0);
-    if (match == null)
-      return diagnose(state);
-    var pos = match[0];
-    pos = _skip_whitespace(state, pos);
-    if (pos == state._end)
-      return match[1];
-    // TODO: Make this complain about expecting end of file.
-    return diagnose(state);
-  }
-
-  diagnose(state) {
-    var message = 'unexpected error';
-    if (!state.max_rule.isEmpty()) {
-      var s = new Set();
-      for (var rule in state.max_rule)
-        s.add(rule.description());
-      var tokens = new List<String>.from(s);
-      tokens.sort((a, b) =>
-                  a.startsWith("'") == b.startsWith("'")
-                      ? a.compareTo(b)
-                      : a.startsWith("'") ? +1 : -1);
-      var expected = Strings.join(tokens, ' or ');
-      var found = state.max_pos == state._end ? 'end of file'
-          : "'${state._text[state.max_pos]}'";
-      message = 'Expected $expected but found $found';
-    }
-    int start = state.max_pos;
-    int end = start;
-    while (start >= 1 && state._text[start - 1] != '\n') --start;
-    while (end < state._text.length && state._text[end] != '\n') ++end;
-    var line = state._text.substring(start, end);
-    var indicator = '';
-    for (var i = 0; i < line.length && start + i < state.max_pos; i++)
-      indicator = indicator + ' ';
-    indicator = indicator + '^';
-    // TODO: Convert to an exception.
-    print(message);
-    print(line);
-    print(indicator);
-    return null;
-  }
-}
-
-class Symbol {
-  final String name;
-  final Grammar grammar;
-  _Rule _rule;
-
-  Symbol(this.name, this.grammar);
-
-  void set def(rule) {
-    assert(_rule == null);  // Assign once.
-    _rule = _compile(rule);
-  }
-
-  toString() => _rule == null ? '<$name>' : '<$name = $_rule>';
-}
-
-
-class _ParserState {
-  _ParserState(this._text, [_Rule whitespace = null]) {
-    _end = this._text.length;
-    whitespaceRule = whitespace;
-    max_rule = [];
-  }
-
-  String _text;
-  int _end;
-
-  //
-  bool inWhitespaceMode = false;
-  _Rule whitespaceRule = null;
-
-  // Used for constructing an error message.
-  int inhibitExpectedTrackingDepth = 0;
-  int max_pos = 0;
-  var max_rule;
-}
-
-/**
- * An interface tag for rules. If this tag is on a rule, then the description()
- * of the rule is something sensible to put in a message.
- */
-interface _Expectable {
-  String description();
-}
-
-class _Rule {
-  const _Rule();
-  // Returns null for a match failure or [pos, ast] for success.
-  match(_ParserState state, int pos) {
-    if (! state.inWhitespaceMode) {
-      pos = _skip_whitespace(state, pos);
-    }
-    return matchAfterWS(state, pos);
-  }
-
-  // Faster entry point for matching a sub-rule that is matched to the start
-  // position of the super-rule.  Whitespace has already been skipped so no need
-  // to try to skip it again.
-  matchAfterWS(_ParserState state, int pos) {
-    if (state.inhibitExpectedTrackingDepth == 0) {
-      // Track position for possible error messaging
-      if (pos > state.max_pos) {
-        // Store position and the rule.
-        state.max_pos = pos;
-        if (this is _Expectable) {
-          state.max_rule = [this];
-        } else {
-          state.max_rule = [];
-        }
-      } else if (pos == state.max_pos) {
-        if (this is _Expectable) {
-          state.max_rule.add(this);
-        }
-      }
-    }
-    // Delegate the matching logic to the the specialized function.
-    return _match(state, pos);
-  }
-
-  // Overridden in subclasses to match the rule.
-  _match(_ParserState state, int pos) => null;
-
-  // Does the rule generate a value (AST) with the match?
-  bool get generatesValue() => false;
-
-  get defaultValue() => null;
-}
-
-int _skip_whitespace(state, pos) {
-  // Returns the next non-whitespace position.
-  // This is done by matching the optional whitespaceRule with the current text.
-  if (state.whitespaceRule == null)
-    return pos;
-  state.inWhitespaceMode = true;
-  state.inhibitExpectedTrackingDepth++;
-  while (true) {
-    var match = state.whitespaceRule.match(state, pos);
-    if (match == null)
-      break;
-    pos = match[0];
-  }
-  state.inWhitespaceMode = false;
-  state.inhibitExpectedTrackingDepth--;
-  return pos;
-}
-
-
-_Rule _compileOptional(rule) {
-  return rule == null ? null : _compile(rule);
-}
-
-_Rule _compile(rule) {
-  if (rule is _Rule)
-    return rule;
-  if (rule is String)
-    return new _StringRule(rule);
-  if (rule is Symbol)
-    return new _SymbolRule(rule);
-  if (rule is RegExp)
-    return new _RegExpRule(rule);
-  if (rule is List) {
-    return _compileMultiRule(
-        rule, true,
-        (compiledRules, valueCount, reducer) =>
-            new _SequenceRule(compiledRules, valueCount, reducer));
-  }
-  throw new Exception('Cannot compile rule: $rule');
-}
-
-class _EndOfInputRule extends _Rule {
-  _match(_ParserState state, int pos) {
-    if (pos == state._end)
-      return [pos, null];
-    return null;
-  }
-
-  toString() => 'END';
-}
-
-class _ErrorRule extends _Rule {
-  String message;
-  _ErrorRule(String this.message);
-  _match(_ParserState state, int pos) {
-    throw new ParseError(message);
-  }
-
-  toString() => 'ERROR($message)';
-}
-
-class _CharCodeRule extends _Rule {
-  Function _predicate;
-  var _name;
-  _CharCodeRule(this._predicate, this._name);
-  _match(_ParserState state, int pos) {
-    if (pos == state._end)
-      return null;
-    int code = state._text.charCodeAt(pos);
-    if (_predicate(code))
-      return [pos + 1, null];
-    return null;
-  }
-
-  toString() => _name == null ? 'CHARCODE($_predicate)' : 'CHARCODE($_name)';
-}
-
-class _AnyCharRule extends _Rule {
-  const _AnyCharRule();
-  _match(_ParserState state, int pos) {
-    if (pos == state._end)
-      return null;
-    return [pos + 1, null];
-  }
-
-  toString() => 'CHAR()';
-}
-
-class _SymbolRule extends _Rule {
-  final Symbol _symbol;
-  _SymbolRule(Symbol this._symbol);
-  _match(_ParserState state, int pos) {
-    if (_symbol._rule == null)
-      throw new Exception("Symbol '${_symbol.name}' is undefined");
-    return _symbol._rule.match(state, pos);
-  }
-
-  bool get generatesValue() => true;
-
-  toString() => '<${_symbol.name}>';
-}
-
-class _SkipRule extends _Rule {
-  // A rule that has no value.
-  _Rule _rule;
-  _SkipRule(_Rule this._rule);
-  _match(_ParserState state, int pos) {
-    var match = _rule.matchAfterWS(state, pos);
-    if (match == null)
-      return null;
-    return [match[0], null];
-  }
-
-  toString() => 'TOKEN($_rule)';
-}
-
-class _StringRule extends _Rule implements _Expectable {
-  final String _string;
-  int _len;
-  _StringRule(this._string) {
-    _len = _string.length;
-  }
-
-  _match(_ParserState state, int pos) {
-    if (pos + _len > state._end)
-      return null;
-    for (int i = 0; i < _len; i++) {
-      if (state._text.charCodeAt(pos + i) != _string.charCodeAt(i))
-        return null;
-    }
-    return [pos + _len, null];
-  }
-
-  //get defaultValue() => _string;
-
-  toString() => '"$_string"';
-
-  description() => "'$_string'";
-}
-
-class _RegExpRule extends _Rule {
-  RegExp _re;
-  _RegExpRule(this._re) {
-    // There is no convenient way to match an anchored substring.
-    throw new Exception('RegExp matching not supported');
-  }
-
-  toString() => '"$_re"';
-}
-
-class _LexicalRule extends _Rule implements _Expectable {
-  final String _name;
-  final _Rule _rule;
-
-  _LexicalRule(String this._name, _Rule this._rule);
-
-  _match(_ParserState state, int pos) {
-    state.inWhitespaceMode = true;
-    state.inhibitExpectedTrackingDepth++;
-    var match = _rule.matchAfterWS(state, pos);
-    state.inhibitExpectedTrackingDepth--;
-    state.inWhitespaceMode = false;
-    return match;
-  }
-
-  toString() => _name;
-
-  description() => _name == null ? '?' : _name;
-}
-
-class _TextValueRule extends _Rule {
-  final _Rule _rule;
-  final _extract;  // Function
-
-  _TextValueRule(_Rule this._rule, Function this._extract);
-
-  _match(_ParserState state, int pos) {
-    var match = _rule.matchAfterWS(state, pos);
-    if (match == null) {
-      return null;
-    }
-    var endPos = match[0];
-    return [endPos, _extract(state._text, pos, endPos)];
-  }
-
-  bool get generatesValue() => true;
-
-  toString() => 'TEXT($_rule)';
-}
-
-_Rule _compileMultiRule(List rules,
-                        bool allowReducer,
-                        finish(compiledRules, valueCount, reducer)) {
-  int valueCount = 0;
-  List compiledRules = new List<_Rule>();
-  Function reducer;
-  for (var rule in rules) {
-    if (reducer != null)
-      throw new Exception('Reducer must be last in sequence: $rule');
-    if (rule is Function) {
-      if (allowReducer)
-        reducer = rule;
-      else
-        throw new Exception('Bad rule: "$rule"');
-    } else {
-      _Rule compiledRule = _compile(rule);
-      if (compiledRule.generatesValue)
-        ++valueCount;
-      compiledRules.add(compiledRule);
-    }
-  }
-  return finish(compiledRules, valueCount, reducer);
-}
-
-String _formatMultiRule(String functor, List rules) {
-  var sb = new StringBuffer(functor);
-  sb.add('(');
-  var separator = '';
-  for (var rule in rules) {
-    sb.add(separator);
-    sb.add(rule);
-    separator = ',';
-  }
-  sb.add(')');
-  return sb.toString();
-}
-
-class _SequenceRule extends _Rule {
-  // This rule matches the component rules in order.
-  final List<_Rule> _rules;
-  final int _generatingSubRules = 0;
-  final Function _reducer;
-  bool _generatesValue;
-  _SequenceRule(List<_Rule> this._rules,
-                int this._generatingSubRules,
-                Function this._reducer) {
-    _generatesValue = _generatingSubRules > 0 || _reducer != null;
-  }
-
-  _match(state, pos) {
-    var sequence = [];
-    for (var rule in _rules) {
-      var match = rule.match(state, pos);
-      if (match == null)
-        return null;
-      if (rule.generatesValue) {
-        var ast = match[1];
-        sequence.add(ast);
-      }
-      pos = match[0];
-    }
-    if (_reducer == null) {
-      if (_generatingSubRules == 0)
-        return [pos, null];
-      if (_generatingSubRules == 1)
-        return [pos, sequence[0]];
-      return [pos, sequence];
-    } else {
-      return [pos, _apply(_reducer, sequence)];
-    }
-  }
-
-  bool get generatesValue() => _generatesValue;
-
-  toString() => _formatMultiRule('SEQ', _rules);
-}
-
-class _ChoiceRule extends _Rule {
-  // This rule matches the first component rule that matches.
-  List<_Rule> _rules;
-  _ChoiceRule(List<_Rule> this._rules);
-
-  _match(state, pos) {
-    for (var rule in _rules) {
-      var match = rule.match(state, pos);
-      if (match != null) {
-        /*
-        if (!rule.generatesValue) {
-          var value = rule.defaultValue;
-          if (value != null)
-            return [match[0], value];
-        }
-        */
-        return match;
-      }
-    }
-    return null;
-  }
-
-  bool get generatesValue() => true;
-
-  toString() => _formatMultiRule('OR', _rules);
-}
-
-class _OptionalRule extends _Rule {
-  _Rule _rule;
-  _OptionalRule(_Rule this._rule);
-  _match(_ParserState state, int pos) {
-    var match = _rule.match(state, pos);
-    if (_rule.generatesValue)
-      return match == null
-          ? [pos, null]
-          : match;
-    return match == null
-        ? [pos, false]
-        : [match[0], true];
-  }
-
-  bool get generatesValue() => true;
-
-  toString() => 'MAYBE($_rule)';
-}
-
-class _ContextRule extends _Rule {
-  _Rule _rule;
-  _ContextRule(_Rule this._rule);
-  _match(_ParserState state, int pos) {
-    // TODO: protect error state.
-    var match = _rule._match(state, pos);
-    if (match == null)
-      return null;
-    return [pos, null];
-  }
-
-  toString() => 'AT($_rule)';
-}
-
-class _NegativeContextRule extends _Rule {
-  _Rule _rule;
-  _NegativeContextRule(_Rule this._rule);
-  _match(_ParserState state, int pos) {
-    // TODO: protect error state.
-    var match = _rule._match(state, pos);
-    if (match == null)
-      return [pos, null];
-    return null;
-  }
-
-  toString() => 'NOT($_rule)';
-}
-
-class _RepeatRule extends _Rule {
-  // Matches zero, one or more items.
-  _Rule _rule;
-  _Rule _separator;
-  int _min;
-
-  _RepeatRule(this._rule, this._separator, this._min);
-
-  _match(state, pos) {
-    // First match.
-    var match = _rule.match(state, pos);
-    if (match == null)
-      if (_min == 0)
-        return [pos, []];
-      else
-        return null;
-    pos = match[0];
-    var result = [match[1]];
-
-    // Subsequent matches:
-    while (true)  {
-      var newPos = pos;
-      if (_separator != null) {
-        match = _separator.match(state, pos);
-        if (match == null)
-          return [pos, result];
-        newPos = match[0];
-      }
-      match = _rule.match(state, newPos);
-      if (match == null)
-        return [pos, result];
-      pos = match[0];
-      result.add(match[1]);
-    }
-  }
-
-  bool get generatesValue() => true;
-
-  toString() => 'MANY(min:$_min, $_rule${_separator==null?'':", sep: $_separator"})';
-}
-
-class _MemoRule extends _Rule {
-  final _Rule _rule;
-
-  var parseInstance;
-
-  // A map from position to result.  Can this be replaced with something
-  // smaller?
-  // TODO: figure out how to discard the map and parseInstance after parsing.
-  Map<int,Object> map;
-
-  _MemoRule(this._rule);
-
-  _match(state, pos) {
-    // See if we are still parsing the same input.  Relies on the fact that the
-    // input is a string and strings are immutable.
-    if (parseInstance !== state._text) {
-      map = new Map<int,Object>();
-      parseInstance = state._text;
-    }
-    // TODO: does this have to check or preserve parse state (like
-    // inWhitespaceMode, error position info etc?)
-    // Stored result can be null (memoized failure).
-    if (map.containsKey(pos)) {
-      return map[pos];
-    }
-    var match = _rule.match(state, pos);
-    map[pos] = match;
-    return match;
-  }
-
-  bool get generatesValue() => _rule.generatesValue;
-
-  toString() => 'MEMO($_rule)';
-}
-
-_apply(fn, List args) {
-  switch (args.length) {
-    case 0: return fn();
-    case 1: return fn(args[0]);
-    case 2: return fn(args[0], args[1]);
-    case 3: return fn(args[0], args[1], args[2]);
-    case 4: return fn(args[0], args[1], args[2], args[3]);
-    case 5: return fn(args[0], args[1], args[2], args[3], args[4]);
-    case 6: return fn(args[0], args[1], args[2], args[3], args[4],
-                      args[5]);
-    case 7: return fn(args[0], args[1], args[2], args[3], args[4],
-                      args[5], args[6]);
-    case 8: return fn(args[0], args[1], args[2], args[3], args[4],
-                      args[5], args[6], args[7]);
-    case 9: return fn(args[0], args[1], args[2], args[3], args[4],
-                      args[5], args[6], args[7], args[8]);
-    case 10: return fn(args[0], args[1], args[2], args[3], args[4],
-                       args[5], args[6], args[7], args[8], args[9]);
-
-    default:
-      throw new Exception('Too many arguments in _apply: $args');
-  }
-}
-
-List _unspread(a,b,c,d,e,f,g,h,i,j,k,l,m,n,o,p,q,r,s,t,u,v,w,x,y,z) {
-  List list = new List();
-  add(element) { if (element != null) list.add(element); }
-  add(a);
-  add(b);
-  add(c);
-  add(d);
-  add(e);
-  add(f);
-  add(g);
-  add(h);
-  add(i);
-  add(j);
-  add(k);
-  add(l);
-  add(m);
-  add(n);
-  add(o);
-  add(p);
-  add(q);
-  add(r);
-  add(s);
-  add(t);
-  add(u);
-  add(v);
-  add(w);
-  add(x);
-  add(y);
-  add(z);
-  return list;
-}