I've been working through the problems on the Project Euler website recently, and as there were some maths functions that I needed over and over I decided to put them into a (C++) utility namespace, MathUtils, which I've put up on GitHub. This post is a short overview of what MathsUtils currently provides. The code should (hopefully) be self explanatory so I'll not provide much more detail here.
(I've also got a class up there called embiguint, which is an unsigned integer that can be arbitrarily large. It has proved useful in its current state but I intend to add a lot more functionality and make it behave more like a built in type at which point I'll do a blog post on it too.)
The functions currently included in MathsUtils are:
template <typename T> std::string
ToAlternateBaseRepresentation(
const T& value, const T& base);
template <typename T> std::vector<T>
GetDivisors(const T& number);
template <typename T> emu64 GetSumOfDivisors(const T& number);
template <typename T> emu64 Factorial(const T& x);
template <typename T> T
PowerOf(const T& base, const T& power);
template <typename T> std::vector<bool>
GetPrimesBoolArrayToN(const T& n);
template <typename T> std::vector<T> GetPrimesToN(const T& n);
I had originally developed the functions in a class with static members but I changed this to a namespace as it seemed more more natural. After all, classes are intended to define how to build objects whereas namespaces are used to group related functionality. In Effective C++, in an item entitled Perfer non-member non-friend functions to member functions, Scott Meyers argues that this approach helps to increase extensiblity and (counter-intuitively) encapsulation.
All the functions are templated as I want to make them as easy to use as possible. There's still lots more I could add to these functions, for example the PowerOf functions only works with non-negative exponents, however each function was written or extended with a particular problem in mind. I'll add more functionality as I need it and in the mean time the functions should throw a useful exception if you ask them to do something they can't do.
There's also lots more I can do with regard to optimisation, and this should give me an opportunity to try out (and learn) some new C++11 features. For example PowerOf and Factorial could benefit from constexpr, although I've just been looking at the release of Visual Studio 2013 and I don't think this feature has made it in. I guess I can achieve the same result with template metaprogramming if I really want quicker run-time code.
Anyway, my MathUtils are in place and poised to help out on more Project Euler problems.
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