テンプレートでたらいまわし（８回目）
継続渡し風味。
#include <iostream> /* True */ class True; /* False */ class False; /* Bool */ template <bool b> struct Bool; template <> struct Bool<true> { typedef True Result; }; template <> struct Bool<false> { typedef False Result; }; /* NullType */ class NullType; /* Typelist */ template <class T, class U> struct Typelist; #define TYPELIST_1(T1) \ Typelist<T1, NullType> #define TYPELIST_2(T1, T2) \ Typelist<T1, TYPELIST_1(T2) > #define TYPELIST_3(T1, T2, T3) \ Typelist<T1, TYPELIST_2(T2, T3) > #define TYPELIST_4(T1, T2, T3, T4) \ Typelist<T1, TYPELIST_3(T2, T3, T4) > #define TYPELIST_5(T1, T2, T3, T4, T5) \ Typelist<T1, TYPELIST_4(T2, T3, T4, T5) > #define TYPELIST_6(T1, T2, T3, T4, T5, T6) \ Typelist<T1, TYPELIST_5(T2, T3, T4, T5, T6) > #define TYPELIST_7(T1, T2, T3, T4, T5, T6, T7) \ Typelist<T1, TYPELIST_6(T2, T3, T4, T5, T6, T7) > #define TYPELIST_8(T1, T2, T3, T4, T5, T6, T7, T8) \ Typelist<T1, TYPELIST_7(T2, T3, T4, T5, T6, T7, T8) > #define TYPELIST_9(T1, T2, T3, T4, T5, T6, T7, T8, T9) \ Typelist<T1, TYPELIST_8(T2, T3, T4, T5, T6, T7, T8, T9) > #define TYPELIST_10(T1, T2, T3, T4, T5, T6, T7, T8, T9, T10) \ Typelist<T1, TYPELIST_9(T2, T3, T4, T5, T6, T7, T8, T9, T10) > /* Append */ template <class T, class U> struct Append; template <class U> struct Append<NullType, U> { typedef U Result; }; template <class T1, class T2, class U> struct Append<Typelist<T1, T2>, U> { typedef Typelist<T1, typename Append<T2, U>::Result> Result; }; /* Int */ template <int x> struct Int { enum { value = x }; }; /* Delay */ template <class TList> struct Delay; /* Force */ class Force; /* Tarai */ template <int x, int y, int z> struct Tarai; template <class TList> struct TaraiBody; template <class X, class Y, class Z, class R> struct Tarai0; template <class Y, class Z, class X, class R> struct Tarai1; template <class Z, class X, class Y, class R> struct Tarai2; template <class B, class Z, class X, class Y, class R> struct Tarai3; template <class X, class Y, class Z, class R> struct Tarai4; template <class Y, class Z, class X, class R> struct Tarai5; template <class Y, class Z, class X, class R> struct Tarai6; template <int x, int y, int z> struct Tarai { typedef TYPELIST_4(Int<0>, Int<x>, Int<y>, Int<z>) TList; enum { value = TaraiBody<TList>::value }; }; template <class X, class Y, class Z, class R> struct Tarai0 { typedef TYPELIST_3(Int<1>, Y, Z) K; typedef TYPELIST_2(Force, X) T; typedef typename Append<T, Typelist<K, R> >::Result TList; enum { value = TaraiBody<TList>::value }; }; template <class Y, class Z, class X, class R> struct Tarai1 { typedef TYPELIST_3(Int<2>, Z, X) K; typedef TYPELIST_2(Force, Y) T; typedef typename Append<T, Typelist<K, R> >::Result TList; enum { value = TaraiBody<TList>::value }; }; template <int x, int y, class Z, class R> struct Tarai2< Z, Int<x>, Int<y>, R > { typedef typename Bool< (x <= y) >::Result B; typedef TYPELIST_5(Int<3>, B, Z, Int<x>, Int<y>) T; typedef typename Append<T, R>::Result TList; enum { value = TaraiBody<TList>::value }; }; template <class X, class Y, class Z, class R> struct Tarai3< True, Z, X, Y, R > { typedef TYPELIST_2(Force, Y) T; typedef typename Append<T, R>::Result TList; enum { value = TaraiBody<TList>::value }; }; template <class X, class Y, class Z, class R> struct Tarai3< False, Z, X, Y, R > { typedef Delay<TYPELIST_4(Int<4>, X, Y, Z)> XX; typedef Delay<TYPELIST_4(Int<4>, Y, Z, X)> YY; typedef Delay<TYPELIST_4(Int<4>, Z, X, Y)> ZZ; typedef TYPELIST_4(Int<0>, XX, YY, ZZ) T; typedef typename Append<T, R>::Result TList; enum { value = TaraiBody<TList>::value }; }; template <class X, class Y, class Z, class R> struct Tarai4 { typedef TYPELIST_3(Int<5>, Y, Z) K; typedef TYPELIST_2(Force, X) T; typedef typename Append<T, Typelist<K, R> >::Result TList; enum { value = TaraiBody<TList>::value }; }; template <int x, class Y, class Z, class R> struct Tarai5< Y, Z, Int<x>, R > { typedef TYPELIST_4(Int<0>, Int<x - 1>, Y, Z) T; typedef typename Append<T, R>::Result TList; enum { value = TaraiBody<TList>::value }; }; template <class X, class Y, class Z, class R> struct TaraiBody< Typelist<Int<0>, Typelist<X, Typelist<Y, Typelist<Z, R> > > > > { enum { value = Tarai0<X, Y, Z, R>::value }; }; template <class X, class Y, class Z, class R> struct TaraiBody< Typelist<Int<1>, Typelist<Y, Typelist<Z, Typelist<X, R> > > > > { enum { value = Tarai1<Y, Z, X, R>::value }; }; template <class X, class Y, class Z, class R> struct TaraiBody< Typelist<Int<2>, Typelist<Z, Typelist<X, Typelist<Y, R> > > > > { enum { value = Tarai2<Z, X, Y, R>::value }; }; template <class X, class Y, class Z, class R, class B> struct TaraiBody< Typelist<Int<3>, Typelist<B, Typelist<Z, Typelist<X, Typelist<Y, R> > > > > > { enum { value = Tarai3<B, Z, X, Y, R>::value }; }; template <class X, class Y, class Z, class R> struct TaraiBody< Typelist<Int<4>, Typelist<X, Typelist<Y, Typelist<Z, R> > > > > { enum { value = Tarai4<X, Y, Z, R>::value }; }; template <class X, class Y, class Z, class R> struct TaraiBody< Typelist<Int<5>, Typelist<Y, Typelist<Z, Typelist<X, R> > > > > { enum { value = Tarai5<Y, Z, X, R>::value }; }; template <int n> struct TaraiBody< Typelist<Force, Typelist<Int<n>, NullType> > > { enum { value = n }; }; template <int n, class R1, class R2> struct TaraiBody< Typelist<Force, Typelist<Int<n>, Typelist<R1, R2> > > > { typedef typename Append< R1, Typelist<Int<n>, R2> >::Result TList; enum { value = TaraiBody<TList>::value }; }; template <class T, class R> struct TaraiBody< Typelist<Force, Typelist<Delay<T>, R> > > { typedef typename Append<T, R>::Result TList; enum { value = TaraiBody<TList>::value }; }; int main(int argc, char *argv[]) { int n = Tarai<12, 6, 0>::value; std::cout << n << std::endl; return 0; }
