| Home | Libraries | People | FAQ | More

## Compile time min/max calculation

The class templates in <boost/integer/static_min_max.hpp> provide a compile-time evaluation of the minimum or maximum of two integers. These facilities are useful for generic programming problems.

### Synopsis

    namespace boost
    {

    typedef implementation-defined static_min_max_signed_type;
    typedef implementation-defined static_min_max_unsigned_type;

    template <static_min_max_signed_type Value1, static_min_max_signed_type Value2 >
        struct static_signed_min;

    template <static_min_max_signed_type Value1, static_min_max_signed_type Value2>
        struct static_signed_max;

    template <static_min_max_unsigned_type Value1, static_min_max_unsigned_type Value2>
        struct static_unsigned_min;

    template <static_min_max_unsigned_type Value1, static_min_max_unsigned_type Value2>
        struct static_unsigned_max;

    }

### Usage

The four class templates provide the combinations for finding the minimum or maximum of two `signed` or `unsigned` (`long`) parameters, Value1 and Value2, at compile-time. Each template has a single static data member, `value`, which is set to the respective minimum or maximum of the template's parameters.

### Example

    #include <boost/integer/static_min_max.hpp>

    template < unsigned long AddendSize1, unsigned long AddendSize2 >
    class adder
    {
    public:
        static  unsigned long  const  addend1_size = AddendSize1;
        static  unsigned long  const  addend2_size = AddendSize2;
        static  unsigned long  const  sum_size = boost::static_unsigned_max<AddendSize1, AddendSize2>::value + 1;

        typedef int  addend1_type[ addend1_size ];
        typedef int  addend2_type[ addend2_size ];
        typedef int  sum_type[ sum_size ];

        void  operator ()( addend1_type const &a1, addend2_type const &a2, sum_type &s ) const;
    };

    //...

    int main()
    {
        int const   a1[] = { 0, 4, 3 };  // 340
        int const   a2[] = { 9, 8 };     //  89
        int         s[ 4 ];
        adder<3,2>  obj;

        obj( a1, a2, s );  // 's' should be 429 or { 9, 2, 4, 0 }
        //...
    }

### Demonstration Program

The program static_min_max_test.cpp is a simplistic demonstration of various comparisons using the compile-time extrema class templates.

### Rationale

Sometimes the minimum or maximum of several values needs to be found for later compile-time processing, e.g. for a bound for another class template.

### Credits

The author of the Boost compile-time extrema class templates is Daryle Walker.