The CrystVector library is not a new array computation library, despite the appearances. ObjCryst++ should used the Blitz++ array library , which yields excellent performance and simple array expressions. Unfortunately, the memory required to compile the library using gcc is far too high to be reasonable when using complex expressions and optimizing code. So until this has changed, The CrystVector and CrystMatrix library have been created, and these emulate (supposedly exactly) the Blitz++ interface (but not the smart handling of mathematical expressions, so pointers must be used). For documentation about these two libraries you should read the Blitz++ documentation. CrystVector and CrystMatrix use the same kind of storage in memory.
You can use CrystArray3D_REAL, CrystArray3D_long,etc... to declare 3D vectors. Macros ensure (well, should) ensure compatibility with Blitz++. (as of april 2001 support of blitz++ is broken).