Specification Meta-Programming

spec.cpp

#define STYPE(type, vt, defcase) template <vt input> struct type { enum { value = (defcase) }; };
#define ITYPE(type, defcase) STYPE(type, int, defcase)
#define SPEC(type, id, result) template <> struct type<id> { enum { value = (result) }; };
#define SVALUE(type, input) type<input>::value

ITYPE(Fib, Fib<input - 1>::value + Fib<input - 2>::value)
SPEC(Fib, 0, 0)
SPEC(Fib, 1, 1)

int main() {
    static_assert(SVALUE(Fib, 10) == 55);

    return 0;
}