This libary aims the provide the neccessary set of classes in order to be able to get some features of C# 3.0, such as extension methods and query expressions. More details of the current idea behind this can be found at the MSDN Linq page.
The System.Query.Sequence class provides methods that work in IEnumerable objects such as arrays and lists:
- Restriction: Where
- Projection: Select
- Partitioning: Take, Skip
- Concatenation: Concat
- Ordering: OrderBy, ThenBy
- Grouping: GroupBy
- Set: Union, Distinct, Intersect, Except
- Element: First, ElementAt
- Quantifiers: All, Any
- Aggregate: Max, Min, Average, Sum, Count, Fold
Most of the functionality is indeed inside this class, except ordering, which occurs inside OrderedSequence. The algorithm used for ordering is the traditional QuickSort.
Any compiler that would like to provide a set of à-la-SQL operators should rely on this library.