I just uploaded a very simple arbitrary precision unsigned integer class to the sandbox ( http://boost-sandbox.sourceforge.net/vault/index.php ). The class is implemented using naive algorithms and is based on std::vector<bool>. Efficiency was absolutely not a concern, the priority was placed on correctness. Without meaning to undermine the impressive work on the expression template big_integer class I thought perhaps programmers would generally prefer a more portable and quickly compiled class. The interface of the type I posted is: class big_uint { typedef big_uint self; public: big_uint(); big_uint(const self& x); big_uint(const std::vector<bool>& x); big_uint(int x); self& operator=(const std::vector<bool>& x); self& operator<<=(int n); self& operator>>=(int n); self operator++(int); self operator--(int); self& operator++(); self& operator--(); self& operator+=(const self& x); self& operator-=(const self& x); self& operator*=(self x); self& operator/=(const self& x); self& operator%=(const self& x); self operator~() const; self& operator&=(self x); self& operator|=(self x); self& operator^=(self x); bool operator[](int n) const; int size() const; unsigned long to_ulong(); friend self operator<<(const self& x, unsigned int n); friend self operator>>(const self& x, unsigned int n); friend self operator+(const self& x, const self& y); friend self operator-(const self& x, const self& y); friend self operator*(const self& x, const self& y); friend self operator/(const self& x, const self& y); friend self operator%(const self& x, const self& y); friend self operator^(const self& x, const self& y); friend self operator&(const self& x, const self& y); friend self operator|(const self& x, const self& y); friend bool operator==(const self& x, const self& y); friend bool operator!=(const self& x, const self& y); friend bool operator>(const self& x, const self& y); friend bool operator<(const self& x, const self& y); friend bool operator>=(const self& x, const self& y); friend bool operator<=(const self& x, const self& y); }; For acceptance into Boost I would guess that this class would have to be much more efficient (though my view is that something that works is better than nothing that runs fast). Unfortunately I can not spend any significant amount of time optimizing it nor doing a proper submission (I would not have time available until around August), so if someone would like to volunteer to take it over, I would appreciate it. Any comments would be most welcome. -- Christopher Diggins http://www.cdiggins.com