This is my review of the XInt library.

- What is your evaluation of the design?

The design looks clean and clear to me. The fact that the default boost::xint::integer provides immediate use of an extended integer is good. The fact that other classes can be created from the integer_t template, to change the functionality of an extended integer in various ways, is fine also. I do not see the need for random number functionality in the library. It also appears to me that prime number generation belongs outside the library. I think the design should be based on providing an extended integer which has the functionality of the C++ built-in integer types, and not try to have other functionality as part of the basic design. Other functionality for working with the extended integer outside of this core emulation of the C++ integer types can be presented as a separate library if necessary in the future. One area that does not follow this emulation of C++ integer types which I would like to see is the ability to convert back and forth to floating point types, since one can do this with built-in integer types. It would be very nice if this were part of the library since converting to C++ integer types and then to a floating point type will fail if the extended integer type is too large for a C++ integer type. But the range of floating point types is large enough for most extended integer values.

- What is your evaluation of the implementation?

I did not look at the code. In general I am not concerned with the implementation details of a library unless I am being asked to change things myself, or I see some bug or slowdown. As an end-user of a library I mainly concern myself with the public and protected functionality of any library components. I feel in general that there is too much of an effort by reviewers to dictate how the internals of a library should be implemented, based on the reviewer's favorite ideas regarding coding. Unless there is a technical issue which will cause the library to not compile or run properly, or to compile or run much slower than need be, I do not see the point of such an effort to pick apart the internal implementation. Of course such technical areas of the internal implementation that causes the aforementioned problems should be critiqued.

- What is your evaluation of the documentation?

The documentation presents a good first page. Things which I feel could be improved are: 1) Features are mentioned, but the "Detailed Usage Information" does not have topics which discuss all those features. I feel that each main feature of a library should have at least a brief discussion before suggesting to look in the reference. 2) Saying to look in the reference section for something more advanced than the basic use of instantiating and using a boost::xint::integer is certainly valid but I would greatly have preferred a more explanatory approach to what is considered "advanced" usage. Again this is similar to 1) in that I feel the documentation should provide as complete a discussion of the features, both simple and advanced, that it can. Furthermore what those "advanced" features are should be enumerated. The reference section is very well done and makes using the integer class fairly easy to understand. However the options to integer_t are not easy to find in the reference section. I think that because this is one of the central concepts of the library, which is that creating an extended integer is flexible, the creation of an extended integer beyond the default boost::xint::integer should be its own topic. I general I think the documentation is laid out well but should be more complete as far as topic explanations.

- What is your evaluation of the potential usefulness of the

library? The potential usefulness is huge. Applications which need integer values beyond the maximum C++ long long values, but which do not want the problems of floating point number calculations, need such a library.

- Did you try to use the library? With what compiler? Did

you have any

problems?

I have tried to use the library with VC++ 10 and gcc-4.5.2 with no problems.

- How much effort did you put into your evaluation? A

glance? A quick

reading? In-depth study?

A slow reading of the documentation.

- Are you knowledgeable about the problem domain?

Yes, fairly knowledgable but not an expert. I vote to have the library accepted into Boost. I feel that if one looks for the "perfect" extended integer library which meets everyone's criteria, then the search will go on forever, while Boost.XInt is certainly good enough in its functionality/design/documentation. I trust that the implementer of the library can work out issues in the future, and I see the library serving a fundamental need now. Edward Diener