The STLplus library is an ongoing project and always will be. Therefore, there is a potential problem with different users using different versions of the library on different parts of a project - the parts may end up being incompatible with each other. There is also a problem whereby software will fail to build if the wrong version of STLplus is used.
For these reasons, version control is used to keep track of the various versions of the library. In fact, there are two layers of version control used - one is a fine-grain control used in development of the library and then there is a second level which is relevant to users of the library.
The library is maintained in a CVS repository for development purposes. This allows every modification to every file in the library to be tracked and versioned. It means that any version of the software at any date since the CVS repository was created can be reproduced. For example, if I wished to use the version that was current on 1 April 2002, I can do that.
This kind of tracking can be useful for the library development but is rather too fine-grain for everyday users who quite frankly don't care what version they're using provided that it works.
The CVS repository is tagged every time I make an official user release. For example, the current version of the library at the time of writing has the tag "stlplus-03-00". This means that checking out on this tag will give you the user's version 3.0 of the library - see below for more on user versions.
The library contains a header in the portability library called version.hpp which defines a macro that contains a version number. This is the coarse-grain version. For example, at the time of writing the macro looked like this:
#define STLPLUS_VERSION "3.0"
This means that the current version is version 3.0. The STLPLUS_VERSION macro was introduced for version 1.0. If your version of the library doesn't have it, then it is an obsolete version, known generically as a "version zero" copy. I cannot support this version because I cannot trace the heritage of such stray copies, so if you have such a copy I recommend you discard it and use an official version.
The SourceForge-hosted open-source version of STLplus starts at version 2.0. Earlier versions were internal (Southampton University) versions. The SourceForge CVS repository only contains version 2.0 onwards; it is a clean start at this version so it is not possible to reproduce any earlier versions.
However, the source code for a particular version number is not fixed. Remember that the library is an ongoing project. There are two reasons why the code might change and the version not:
The process that I use for making releases is as follows:
I develop new features on a development copy of the library. This is known as the "latest" copy. When I am satisfied that this version has reached a level of stability that makes it a candidate for an official release, I freeze the source code and make an official release of it. This is the end of development for that version number excepting minor bug-fixes.
Once an official release is made, the version number of the development copy of the library is incremented. This results in a new version which has not been released officially yet. This becomes the new development version which I will then use to develop more features or packages. Nevertheless, if you want the very latest copy of STLplus, you can get a copy of this version by obtaining the "latest" version. Bear in mind that this version can change a lot because it is the development version. It can also get broken because of mistakes on my part. Therefore, if you don't want to be affected by these changes, stick to an official release. For example, at the time of writing, version 3.0 was the last official release and so the development copy is version 3.1.