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petitparser/lib/src/core/parsers.dart

-part of petitparser;
-
-/**
- * Returns a parser that consumes nothing and succeeds.
- *
- * For example, `char('a').or(epsilon())` is equivalent to
- * `char('a').optional()`.
- */
-Parser epsilon([result]) => new EpsilonParser(result);
-
-/**
- * A parser that consumes nothing and succeeds.
- */
-class EpsilonParser extends Parser {
-  final _result;
-
-  EpsilonParser(this._result);
-
-  @override
-  Result parseOn(Context context) => context.success(_result);
-
-  @override
-  Parser copy() => new EpsilonParser(_result);
-
-  @override
-  bool hasEqualProperties(Parser other) {
-    return other is EpsilonParser
-        && super.hasEqualProperties(other)
-        && _result == other._result;
-  }
-}
-
-/**
- * Returns a parser that consumes nothing and fails.
- *
- * For example, `failure()` always fails, no matter what input it is given.
- */
-Parser failure([String message = 'unable to parse']) {
-  return new FailureParser(message);
-}
-
-/**
- * A parser that consumes nothing and fails.
- */
-class FailureParser extends Parser {
-  final String _message;
-
-  FailureParser(this._message);
-
-  @override
-  Result parseOn(Context context) => context.failure(_message);
-
-  @override
-  String toString() => '${super.toString()}[$_message]';
-
-  @override
-  Parser copy() => new FailureParser(_message);
-
-  @override
-  bool hasEqualProperties(Parser other) {
-    return other is FailureParser
-        && super.hasEqualProperties(other)
-        && _message == other._message;
-  }
-}
-
-/**
- * Returns a parser that is not defined, but that can be set at a later
- * point in time.
- *
- * For example, the following code sets up a parser that points to itself
- * and that accepts a sequence of a's ended with the letter b.
- *
- *     var p = undefined();
- *     p.set(char('a').seq(p).or(char('b')));
- */
-SettableParser undefined([String message = 'undefined parser']) {
-  return failure(message).settable();
-}
-
-/**
- * A parser that is not defined, but that can be set at a later
- * point in time.
- */
-class SettableParser extends DelegateParser {
-  SettableParser(parser) : super(parser);
-
-  /**
-   * Sets the receiver to delegate to [parser].
-   */
-  void set(Parser parser) => replace(children[0], parser);
-
-  @override
-  Parser copy() => new SettableParser(_delegate);
-}