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petitparser/lib/src/core/combinators.dart

-part of petitparser;
-
-/**
- * A parser that delegates to another one. Normally users do not need to
- * directly use a delegate parser.
- */
-class DelegateParser extends Parser {
-  Parser _delegate;
-
-  DelegateParser(this._delegate);
-
-  @override
-  Result parseOn(Context context) {
-    return _delegate.parseOn(context);
-  }
-
-  @override
-  List<Parser> get children => [_delegate];
-
-  @override
-  void replace(Parser source, Parser target) {
-    super.replace(source, target);
-    if (_delegate == source) {
-      _delegate = target;
-    }
-  }
-
-  @override
-  Parser copy() => new DelegateParser(_delegate);
-}
-
-/**
- * A parser that succeeds only at the end of the input.
- */
-class EndOfInputParser extends DelegateParser {
-  final String _message;
-
-  EndOfInputParser(parser, this._message) : super(parser);
-
-  @override
-  Result parseOn(Context context) {
-    var result = _delegate.parseOn(context);
-    if (result.isFailure || result.position == result.buffer.length) {
-      return result;
-    }
-    return result.failure(_message, result.position);
-  }
-
-  @override
-  String toString() => '${super.toString()}[$_message]';
-
-  @override
-  Parser copy() => new EndOfInputParser(_delegate, _message);
-
-  @override
-  bool hasEqualProperties(Parser other) {
-    return other is EndOfInputParser && super.hasEqualProperties(other)
-        && _message == other._message;
-  }
-}
-
-/**
- * The and-predicate, a parser that succeeds whenever its delegate does, but
- * does not consume the input stream [Parr 1994, 1995].
- */
-class AndParser extends DelegateParser {
-  AndParser(parser) : super(parser);
-
-  @override
-  Result parseOn(Context context) {
-    var result = _delegate.parseOn(context);
-    if (result.isSuccess) {
-      return context.success(result.value);
-    } else {
-      return result;
-    }
-  }
-
-  @override
-  Parser copy() => new AndParser(_delegate);
-}
-
-/**
- * The not-predicate, a parser that succeeds whenever its delegate does not,
- * but consumes no input [Parr 1994, 1995].
- */
-class NotParser extends DelegateParser {
-  final String _message;
-
-  NotParser(parser, this._message) : super(parser);
-
-  @override
-  Result parseOn(Context context) {
-    var result = _delegate.parseOn(context);
-    if (result.isFailure) {
-      return context.success(null);
-    } else {
-      return context.failure(_message);
-    }
-  }
-
-  @override
-  String toString() => '${super.toString()}[$_message]';
-
-  @override
-  Parser copy() => new NotParser(_delegate, _message);
-
-  @override
-  bool hasEqualProperties(Parser other) {
-    return other is NotParser
-        && super.hasEqualProperties(other)
-        && _message == other._message;
-  }
-}
-
-/**
- * A parser that optionally parsers its delegate, or answers nil.
- */
-class OptionalParser extends DelegateParser {
-  final _otherwise;
-
-  OptionalParser(parser, this._otherwise) : super(parser);
-
-  @override
-  Result parseOn(Context context) {
-    var result = _delegate.parseOn(context);
-    if (result.isSuccess) {
-      return result;
-    } else {
-      return context.success(_otherwise);
-    }
-  }
-
-  @override
-  Parser copy() => new OptionalParser(_delegate, _otherwise);
-
-  @override
-  bool hasEqualProperties(Parser other) {
-    return other is OptionalParser
-        && super.hasEqualProperties(other)
-        && _otherwise == other._otherwise;
-  }
-}
-
-/**
- * Abstract parser that parses a list of things in some way.
- */
-abstract class ListParser extends Parser {
-  final List<Parser> _parsers;
-
-  ListParser(this._parsers);
-
-  @override
-  List<Parser> get children => _parsers;
-
-  @override
-  void replace(Parser source, Parser target) {
-    super.replace(source, target);
-    for (var i = 0; i < _parsers.length; i++) {
-      if (_parsers[i] == source) {
-        _parsers[i] = target;
-      }
-    }
-  }
-}
-
-/**
- * A parser that uses the first parser that succeeds.
- */
-class ChoiceParser extends ListParser {
-  factory ChoiceParser(Iterable<Parser> parsers) {
-    return new ChoiceParser._(new List.from(parsers, growable: false));
-  }
-
-  ChoiceParser._(parsers) : super(parsers);
-
-  @override
-  Result parseOn(Context context) {
-    var result;
-    for (var i = 0; i < _parsers.length; i++) {
-      result = _parsers[i].parseOn(context);
-      if (result.isSuccess) {
-        return result;
-      }
-    }
-    return result;
-  }
-
-  @override
-  Parser or(Parser other) {
-    return new ChoiceParser(new List()
-      ..addAll(_parsers)
-      ..add(other));
-  }
-
-  @override
-  Parser copy() => new ChoiceParser(_parsers);
-}
-
-/**
- * A parser that parses a sequence of parsers.
- */
-class SequenceParser extends ListParser {
-  factory SequenceParser(Iterable<Parser> parsers) {
-    return new SequenceParser._(new List.from(parsers, growable: false));
-  }
-
-  SequenceParser._(parsers) : super(parsers);
-
-  @override
-  Result parseOn(Context context) {
-    var current = context;
-    var elements = new List(_parsers.length);
-    for (var i = 0; i < _parsers.length; i++) {
-      var result = _parsers[i].parseOn(current);
-      if (result.isFailure) {
-        return result;
-      }
-      elements[i] = result.value;
-      current = result;
-    }
-    return current.success(elements);
-  }
-
-  @override
-  Parser seq(Parser other) {
-    return new SequenceParser(new List()
-      ..addAll(_parsers)
-      ..add(other));
-  }
-
-  @override
-  Parser copy() => new SequenceParser(_parsers);
-}