327 lines
7.9 KiB
C++
327 lines
7.9 KiB
C++
#include<iostream>
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namespace S { //S-Expressions
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template<int Name> struct Atom {const static int name = Name;};
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#define name(N,S) template<> struct Atom<-N> {const static int name = -N; char* str = #S;}; Atom<-N> typedef S;
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name( 1,NIL)
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name( 2,CONS)
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name( 3,ATOM)
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name( 4,T)
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name( 5,F)
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name( 6,CAR)
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name( 7,CDR)
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name( 8,LAMBDA)
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name( 9,LABEL)
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name(10,QUOTE)
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name(11,COND)
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name(12,EQ)
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name(13,EQUAL)
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name(14,LIST)
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#undef name
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// cons
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template<typename L, typename R>
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struct Cons {};
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// bool to Symbolic Bool conversion
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template<bool B>
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struct ToSbool {};
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template<>
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struct ToSbool<true> {
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T typedef value;
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};
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template<>
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struct ToSbool<false> {
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F typedef value;
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};
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// Sybolic Bool to bool conversion
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template<typename B>
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struct ToBool {};
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template<>
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struct ToBool<T> {
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const static bool value = true;
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};
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template<>
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struct ToBool<F> {
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const static bool value = false;
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};
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}
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namespace M { //M-Expressions
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// atom
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template<typename E>
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struct Atom {
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S::F typedef value;
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};
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template<int I>
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struct Atom<S::Atom<I> > {
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S::T typedef value;
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};
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// car
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template<typename E>
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struct Car {};
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template<typename A, typename D>
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struct Car<S::Cons<A, D> > {
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A typedef value;
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};
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// cdr
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template<typename E>
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struct Cdr {};
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template<typename A, typename D>
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struct Cdr<S::Cons<A, D> > {
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D typedef value;
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};
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// eq
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template<typename E1, typename E2>
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struct Eq {};
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template<int I1, int I2>
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struct Eq<S::Atom<I1>, S::Atom<I2> > {
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S::F typedef value;
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};
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template<int I>
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struct Eq<S::Atom<I>, S::Atom<I> > {
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S::T typedef value;
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};
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// equal
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template<typename E1, typename E2>
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struct Equal {
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S::F typedef value;
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};
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template<typename A1, typename A2, typename D1, typename D2>
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struct Equal<S::Cons<A1, D1>, S::Cons<A2, D2> > {
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typename Equal<A1, A2>::value typedef EA;
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typename Equal<D1, D2>::value typedef ED;
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typename S::ToSbool<
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S::ToBool<EA>::value && S::ToBool<ED>::value
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>::value typedef value;
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};
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template<int I1, int I2>
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struct Equal<S::Atom<I1>, S::Atom<I2> > {
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typename Eq<S::Atom<I1>, S::Atom<I2> >::value typedef value;
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};
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// eval (prototype)
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template<typename X, typename E>
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struct Eval {};
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// evlist
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template<typename L, typename E>
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struct Evlist {};
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template<typename E>
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struct Evlist<S::NIL, E> {
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S::NIL typedef value;
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};
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template<typename H, typename R, typename E>
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struct Evlist<S::Cons<H, R>, E> {
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S::Cons<typename Eval<H, E>::value, typename Evlist<R, E>::value> typedef value;
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};
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// assoc
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template<typename X, typename E>
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struct Assoc {};
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template<typename X, typename V, typename R>
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struct Assoc<X, S::Cons<S::Cons<X, V>, R> > {
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V typedef value;
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};
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template<typename X, typename WX, typename WV, typename R>
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struct Assoc<X, S::Cons<S::Cons<WX, WV>, R> > {
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typename Assoc<X, R>::value typedef value;
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};
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// evcond
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template<typename C, typename E>
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struct Evcond {};
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template<typename V, typename R, typename E>
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struct Evcond<S::Cons<S::Cons<S::T, S::Cons<V, S::NIL> >, R>, E> {
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typename Eval<V, E>::value typedef value;
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};
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template<typename V, typename R, typename E>
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struct Evcond<S::Cons<S::Cons<S::F, S::Cons<V, S::NIL> >, R>, E> {
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typename Evcond<R, E>::value typedef value;
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};
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template<typename Tr, typename V, typename R, typename E>
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struct Evcond<S::Cons<S::Cons<Tr, S::Cons<V, S::NIL> >, R>, E> {
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typename Evcond<S::Cons<S::Cons<typename Eval<Tr, E>::value, S::Cons<V, S::NIL> >, R>, E>::value typedef value;
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};
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// pairlist
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template<typename As, typename Ds, typename E>
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struct Pairlist {};
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template<typename Ds, typename E>
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struct Pairlist<S::NIL, Ds, E> {
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E typedef value;
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};
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template<typename A, typename RA, typename D, typename RD, typename E>
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struct Pairlist<S::Cons<A, RA>, S::Cons<D, RD>, E> {
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S::Cons<S::Cons<A, D>, typename Pairlist<RA, RD, E>::value> typedef value;
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};
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// eval
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template<int I, typename E>
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struct Eval<S::Atom<I>, E> {
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typename Assoc<S::Atom<I>, E>::value typedef value;
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};
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template<typename R, typename E>
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struct Eval<S::Cons<S::QUOTE, R>, E> {
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typename Car<R>::value typedef value;
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};
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template<typename R, typename E>
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struct Eval<S::Cons<S::ATOM, R>, E> {
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typename Atom<typename Eval<typename Car<R>::value, E>::value>::value typedef value;
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};
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template<typename R, typename E>
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struct Eval<S::Cons<S::COND, R>, E> {
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typename Evcond<R, E>::value typedef value;
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};
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template<typename R, typename E>
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struct Eval<S::Cons<S::EQ, R>, E> {
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typename Eq<
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typename Eval<typename Car<R>::value, E>::value,
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typename Eval<typename Car<typename Cdr<R>::value>::value, E>::value
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>::value typedef value;
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};
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template<typename R, typename E>
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struct Eval<S::Cons<S::EQUAL, R>, E> {
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typename Equal<
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typename Eval<typename Car<R>::value, E>::value,
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typename Eval<typename Car<typename Cdr<R>::value>::value, E>::value
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>::value typedef value;
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};
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template<typename R, typename E>
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struct Eval<S::Cons<S::CAR, R>, E> {
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typename Car<
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typename Eval<typename Car<R>::value, E>::value
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>::value typedef value;
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};
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template<typename R, typename E>
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struct Eval<S::Cons<S::CDR, R>, E> {
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typename Cdr<
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typename Eval<typename Car<R>::value, E>::value
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>::value typedef value;
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};
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template<typename R, typename E>
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struct Eval<S::Cons<S::CONS, R>, E> {
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S::Cons<
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typename Eval<typename Car<R>::value, E>::value,
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typename Eval<typename Car<typename Cdr<R>::value>::value, E>::value
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> typedef value;
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};
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template<typename R, typename E>
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struct Eval<S::Cons<S::LIST, R>, E> {
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typename Evlist<R, E>::value typedef value;
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};
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template<int N, typename R, typename E>
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struct Eval<S::Cons<S::Atom<N>, R>, E> {
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typename Eval<S::Cons<typename Eval<S::Atom<N>, E>::value, R>, E>::value typedef value;
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};
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template<typename Names, typename Body, typename R, typename E>
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struct Eval<S::Cons<S::Cons<S::LAMBDA, S::Cons<Names, S::Cons<Body, S::NIL> > >, R>, E> {
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typename Eval<
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Body,
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typename Pairlist<Names, typename Evlist<R, E>::value, E>::value
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>::value typedef value;
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};
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template<int N, typename Body, typename R, typename E>
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struct Eval<S::Cons<S::Cons<S::LABEL, S::Cons<S::Atom<N>, S::Cons<Body, S::NIL> > >, R>, E> {
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typename Eval<
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S::Cons<Body, R>,
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S::Cons<S::Cons<S::Atom<N>, Body>, E>
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>::value typedef value;
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};
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}
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int main() {
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/* Human-readable version of the following expression
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Eval[
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((LABEL Atom0
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(LAMBDA (Atom1 Atom2) (COND
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((EQUAL Atom1 'NIL) Atom2)
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(T (CONS (CAR Atom1) (Atom0 (CDR Atom1) Atom2)))
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)))
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'(Atom3 Atom4)
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'(Atom5 Atom6));
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NIL
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]
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*/
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typename M::Eval<
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S::Cons<
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S::Cons<
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S::LABEL,
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S::Cons<
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S::Atom<0>,//concat
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S::Cons<
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S::Cons<
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S::LAMBDA,
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S::Cons<
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S::Cons<
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S::Atom<1>,
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S::Cons<
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S::Atom<2>,
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S::NIL> >,
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S::Cons<
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S::Cons<
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S::COND,
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S::Cons<
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S::Cons<
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S::Cons<
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S::EQUAL,
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S::Cons<
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S::Atom<1>,
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S::Cons<
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S::Cons<
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S::QUOTE,
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S::Cons<
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S::NIL,
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S::NIL> >,
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S::NIL> > >,
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S::Cons<
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S::Atom<2>,
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S::NIL> >,
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S::Cons<
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S::Cons<
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S::T,
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S::Cons<
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S::Cons<
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S::CONS,
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S::Cons<
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S::Cons<
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S::CAR,
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S::Cons<
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S::Atom<1>,
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S::NIL> >,
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S::Cons<
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S::Cons<
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S::Atom<0>,
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S::Cons<
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S::Cons<
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S::CDR,
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S::Cons<
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S::Atom<1>,
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S::NIL> >,
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S::Cons<
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S::Atom<2>,
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S::NIL> > >,
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S::NIL> > >,
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S::NIL> >,
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S::NIL> > >,
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S::NIL> > >,
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S::NIL> > >,
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S::Cons<
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S::Cons<
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S::QUOTE,
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S::Cons<
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S::Cons<
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S::Atom<3>,
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S::Cons<
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S::Atom<4>,
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S::NIL> >,
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S::NIL> >,
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S::Cons<
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S::Cons<
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S::QUOTE,
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S::Cons<
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S::Cons<
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S::Atom<5>,
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S::Cons<
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S::Atom<6>,
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S::NIL> >,
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S::NIL> >,
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S::NIL> > >,
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S::NIL
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>::value typedef X; //X is the result of the computation
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X::print_by_error; //print_by_error doesn't exist, so a compiler with good feedback will represent the type "X" in an error
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return 0;
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}
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