#include <iostream>

//abs
template <long x, typename enabled=void>
struct tabs { const static long value = x; };
template <long x>
struct tabs<x,typename enable_if_c<(x < 0)>::type> { const static long value = -x; };

//max
template <long x, long y, typename enabled=void>
struct tmax { const static long value = x; };
template <long x, long y>
struct tmax<x,y,typename enable_if_c<(y > x)>::type> { const static long value = y; };

//min
template <long x, long y, typename enabled=void>
struct tmin { const static long value = x; };
template <long x, long y>
struct tmin<x,y,typename enable_if_c<(y < x)>::type> { const static long value = y; };

int main() {
    tabs<-4>::value == 4;
    tabs<4>::value == 4;

    tmax<4,7>::value == 7

    tmin<4,7>::value == 4
}