libefgy is a set of C++ headers containing lots of templates loosely related to maths. The headers include templates for fractional arithmetic, big integers (and thus "big fractions"), calculating π, e, and some calculations with those (for trigonometrics), matrix manipulations, tuples, polar and Euclidian spaces in arbitrary dimensions, (perspective) projections, colour space manipulations in RGB and HSL, and assorted other things.
Controlled Variables implements secure basic types in C++. It provides C++ templates that give you the ability to control the initialization of your basic C types (i.e. char, int, long long, etc.). In particular, it allows you to avoid forgetting to initialize variable members, since these variables cannot be initialized where declared. Controlled Variables can be used wherever you declare a basic type variable without immediately initializing it (and limited controlled variables where a bounded value is used).