CSTL

Without comparing source code, can anyway say whether these are separate projects and which is considered to be in better condition or actively maintained.

NSTL is located on CodePlex here and is maintained by a different person, "Andy M".
http://www.codeplex.com/nstl

I have looked at NSTL. NSTL and CSTL are separate projects. Since I am the creator of CSTL, I am obviously biased, but these are the differences that I see

- NSTL has more recent additions.
- NSTL has more collections at the moment.
- It looks to me that CSTL has more algorithms implemented, but not by much.
- NSTL is designed to be a direct port of an STL implementation to C# and .NET. CSTL is STL'ish, but I have opted to go in a different direction in some areas. Namely,
- Algorithms that take IList<T> and IEnumerable<T> methods
- Overloads that take IComparer<T> and Comparison<T> where appropriate
- Heavy use of anonymous methods as predicates and function objects.

NSTL looks good. I think the maintainer knows what he is doing. However, I think the algorithms in CSTL are easier to work with from C# because of what I mention above. See the CSTL readme for more about the philosophy behind the library.

H^2