/// <summary>
/// Matches the left parser and the right parser in any order and yields the matches from both in a concatenated sequence,
/// or yields no matches if either the first or second parser has no matches.
/// </summary>
/// <typeparam name="TSource">The type of the source elements.</typeparam>
/// <typeparam name="TResult">The type of the elements that are generated from parsing the source elements.</typeparam>
/// <param name="parser">A parser to be matched, before or after the other parser.</param>
/// <param name="otherParser">The other parser to be matched, before or after the first parser.</param>
/// <returns>A parser that yields a concatenated sequence of matches from the first parser and the second parser in any order,
/// or no matches if either the first or second parser has no matches.</returns>
public static IObservableParser <TSource, IObservable <TResult> > AndUnordered <TSource, TResult>(
this IObservableParser <TSource, TResult> parser,
IObservableParser <TSource, IObservable <TResult> > otherParser)
{
Contract.Requires(parser != null);
Contract.Requires(otherParser != null);
Contract.Ensures(Contract.Result <IObservableParser <TSource, IObservable <TResult> > >() != null);
// Optimization similar to And is inappropriate here because a grammar of sequential AndUnordered parsers actually implies
// an order that must be respected between each unordered group. For example, a parser grammar such as "{12}{34}", where
// each character within {} is combined using AndUnordered, must match any of the following input sequences: "1234", "2134",
// "1243", "2143"; however, it must not match any of the following input sequences: "3124", "4321", "3241", "4123", etc.
return(AllUnordered(new[] { parser.Amplify(), otherParser }));
}
/// <summary>
/// Matches the left parser followed by the right parser and yields the matches from both in a concatenated sequence,
/// or yields no matches if either the first or second parser has no matches.
/// </summary>
/// <typeparam name="TSource">The type of the source elements.</typeparam>
/// <typeparam name="TResult">The type of the elements that are generated from parsing the source elements.</typeparam>
/// <param name="parser">The parser to be matched first.</param>
/// <param name="nextParser">The parser to be matched after the first <paramref name="parser"/>.</param>
/// <returns>A parser that yields a concatenated sequence of matches from the first parser followed by the second parser,
/// or no matches if either the first or second parser has no matches.</returns>
public static IObservableParser <TSource, IObservable <TResult> > And <TSource, TResult>(
this IObservableParser <TSource, TResult> parser,
IObservableParser <TSource, IObservable <TResult> > nextParser)
{
Contract.Requires(parser != null);
Contract.Requires(nextParser != null);
Contract.Ensures(Contract.Result <IObservableParser <TSource, IObservable <TResult> > >() != null);
// The following code is an optimization that combines nested Ands (on the right side) into a single And.
// It's not possible for this overload to be called with a nested And on the left side because And always
// produces IEnumerable<TResult> and this overload defines the left side as a scalar TResult, thus the
// compiler will choose a different overload of And when nested on the left.
var right = new List <IObservableParser <TSource, TResult> >();
var rightMany = new List <IObservableParser <TSource, IObservable <TResult> > >();
var nestedRight = nextParser as AllObservableParser <TSource, TResult>;
var nestedRightMany = nextParser as AllManyObservableParser <TSource, TResult>;
if (nestedRight == null && nestedRightMany == null)
{
rightMany.Add(nextParser);
}
else if (nestedRight != null)
{
right.AddRange(nestedRight.Parsers);
}
else
{
rightMany.AddRange(nestedRightMany.Parsers);
}
// If the left or right side has no parsers then the parse operation must fail, but must be evaluated anyway.
// e.g., Given the nested combination of someParser.And(All(emptyParserList)), this is gauranteed to fail
// on All, so it seems futile to even attempt parsing the left side; however, since there may be side-effects
// the left side must be parsed anyway. There are several nested parser combinations that meet this criteria.
// Futhermore, all combinations must not throw an exception.
// In any possible case where the left or right side doesn't have any parsers, the parse operation must
// result in a parse failure (i.e., no results) - not an exception.
if (right.Count > 0)
{
return(All(new[] { parser }.Concat(right)));
}
else
{
return(All(new[] { parser.Amplify() }.Concat(rightMany)));
}
}
/// <summary>
/// Matches the specified <paramref name="parser"/> the specified number of times.
/// </summary>
/// <typeparam name="TSource">The type of the source elements.</typeparam>
/// <typeparam name="TResult">The type of the elements that are generated from parsing the source elements.</typeparam>
/// <param name="parser">The parser to be matched.</param>
/// <param name="count">The specified number of times to match the specified <paramref name="parser"/>.</param>
/// <returns>A parser that matches the specified <paramref name="parser"/> the specified number of times.</returns>
public static IObservableParser <TSource, IObservable <TResult> > Exactly <TSource, TResult>(
this IObservableParser <TSource, TResult> parser,
int count)
{
Contract.Requires(parser != null);
Contract.Requires(count >= 0);
Contract.Ensures(Contract.Result <IObservableParser <TSource, IObservable <TResult> > >() != null);
if (count == 0)
{
return(parser.Yield(_ => ObservableParseResult.ReturnSuccessMany <TResult>(length: 0)));
}
else if (count == 1)
{
// Profiling has shown this to be about 50% faster than Repeat(parser, 1).All()
return(parser.Amplify());
}
else if (parser is IObservableParserCursor <TSource> )
{
/* Profiling has shown this to be exponentially faster in next.Exactly(largeN) queries for Ix.
* It hasn't been profiled in Rx, but I'm assuming that for similar reasons as Ix it would prove
* to be exponentially faster. Furthermore, due to the extra plumbing in Rx that's being avoided
* by this optimization, it may have even greater gains than Ix.
*/
return(parser.Yield <TSource, TResult, IObservable <TResult> >(
"Exactly",
source =>
from list in source.Take(count).ToList()
where list.Count == count
select ParseResult.Create(list.Cast <TResult>().ToObservable(Scheduler.Immediate), count)));
}
else
{
return(System.Linq.Enumerable.Repeat(parser, count).All());
}
}