Tuplr -> Resp (RESource Processing).

git-svn-id: http://svn.drobilla.net/resp/resp@252 ad02d1e2-f140-0410-9f75-f8b11f17cedd

1 files changed, 727 insertions, 0 deletions

diff --git a/src/resp.hpp b/src/resp.hpp
new file mode 100644
index 0000000..81574e9
--- /dev/null
+++ b/src/resp.hpp
@@ -0,0 +1,727 @@
+/* Resp: A programming language
+ * Copyright (C) 2008-2009 David Robillard <dave@drobilla.net>
+ *
+ * Resp is free software: you can redistribute it and/or modify it under
+ * the terms of the GNU Affero General Public License as published by the
+ * Free Software Foundation, either version 3 of the License, or (at your
+ * option) any later version.
+ *
+ * Resp is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
+ * or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Affero General
+ * Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with Resp.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+/** @file
+ * @brief Interface and type definitions
+ */
+
+#ifndef RESP_HPP
+#define RESP_HPP
+
+#include <stdarg.h>
+#include <stdint.h>
+#include <string.h>
+#include <iostream>
+#include <list>
+#include <map>
+#include <set>
+#include <sstream>
+#include <string>
+#include <vector>
+#include <boost/format.hpp>
+
+#define FOREACH(IT, i, c)  for (IT i = (c).begin(); i != (c).end(); ++i)
+#define FOREACHP(IT, i, c) for (IT i = (c)->begin(); i != (c)->end(); ++i)
+#define THROW_IF(cond, error, ...) { if (cond) throw Error(error, __VA_ARGS__); }
+
+using namespace std;
+using boost::format;
+
+
+/***************************************************************************
+ * Basic Utility Classes                                                   *
+ ***************************************************************************/
+
+/// Location in textual code
+struct Cursor {
+	Cursor(const string& n="", unsigned l=1, unsigned c=0) : name(n), line(l), col(c) {}
+	operator bool() const { return !(line == 1 && col == 0); }
+	string str() const { return (format("%1%:%2%:%3%") % name % line % col).str(); }
+	string   name;
+	unsigned line;
+	unsigned col;
+};
+
+/// Compiler error
+struct Error {
+	Error(Cursor c, const string& m) : loc(c), msg(m) {}
+	const string what() const { return (loc ? loc.str() + ": " : "") + "error: " + msg; }
+	const Cursor loc;
+	const string msg;
+};
+
+/// Generic Lexical Environment
+template<typename K, typename V>
+struct Env : public list< vector< pair<K,V> > > {
+	typedef vector< pair<K,V> > Frame;
+	Env() : list<Frame>(1) {}
+	virtual ~Env() {}
+	virtual void push(Frame f=Frame()) { list<Frame>::push_front(f); }
+	virtual void pop()                 { list<Frame>::pop_front(); }
+	const V& def(const K& k, const V& v) {
+		for (typename Frame::iterator b = this->begin()->begin(); b != this->begin()->end(); ++b)
+			if (b->first == k)
+				return (b->second = v);
+		this->front().push_back(make_pair(k, v));
+		return v;
+	}
+	V* ref(const K& key) {
+		for (typename Env::iterator f = this->begin(); f != this->end(); ++f)
+			for (typename Frame::iterator b = f->begin(); b != f->end(); ++b)
+				if (b->first == key)
+					return &b->second;
+		return NULL;
+	}
+	bool topLevel(const K& key) const {
+		for (typename Frame::const_iterator b = this->back().begin(); b != this->back().end(); ++b)
+			if (b->first == key)
+				return true;
+		return false;
+	}
+};
+
+template<typename K, typename V>
+ostream& operator<<(ostream& out, const Env<K,V>& env) {
+	out << "(Env" << endl;
+	for (typename Env<K,V>::const_reverse_iterator f = env.rbegin(); f != env.rend(); ++f) {
+		out << "  (" << endl;
+		for (typename Env<K,V>::Frame::const_iterator b = f->begin(); b != f->end(); ++b)
+			cout << "    " << b->first << " " << b->second << endl;
+		out << "  )" << endl;
+	}
+	out << ")" << endl;
+	return out;
+}
+
+
+/***************************************************************************
+ * Lexer: Text (istream) -> S-Expressions (SExp)                           *
+ ***************************************************************************/
+
+class AST;
+AST* readExpression(Cursor& cur, std::istream& in);
+
+
+/***************************************************************************
+ * Backend Types                                                           *
+ ***************************************************************************/
+
+typedef void* CVal;  ///< Compiled value (opaque)
+typedef void* CFunc; ///< Compiled function (opaque)
+
+
+/***************************************************************************
+ * Garbage Collection                                                      *
+ ***************************************************************************/
+
+struct Object;
+
+/// Garbage collector
+struct GC {
+	typedef std::list<const Object*> Roots;
+	typedef std::list<Object*>       Heap;
+	GC(size_t pool_size);
+	~GC();
+	void* alloc(size_t size);
+	void  collect(const Roots& roots);
+	void  addRoot(const Object* obj) { assert(obj); _roots.push_back(obj); }
+	void  lock() { _roots.insert(_roots.end(), _heap.begin(), _heap.end()); }
+	const Roots& roots() const { return _roots; }
+private:
+	void* _pool;
+	Heap  _heap;
+	Roots _roots;
+};
+
+/// Garbage collected object (including AST and runtime data)
+struct Object {
+	enum Tag { OBJECT = 123, AST = 456 };
+
+	struct Header {
+		uint32_t mark;
+		uint32_t tag;
+	};
+
+	inline Tag  tag()        const { return (Tag)header()->tag; }
+	inline void tag(Tag t)         { header()->tag = t; }
+	inline bool marked()     const { return header()->mark != 0; }
+	inline void mark(bool b) const { header()->mark = (b ? 1 : 0); }
+
+	static void* operator new(size_t size)  { return pool.alloc(size); }
+	static void  operator delete(void* ptr) {}
+
+	// Memory used with placement new MUST always be allocated with pool.alloc!
+	static void* operator new(size_t size, void* ptr) { return ptr; }
+
+	static GC pool;
+
+private:
+	/// Always allocated with pool.alloc, so this - sizeof(Header) is a valid Header*.
+	inline Header* header() const { return (Header*)((char*)this - sizeof(Header)); }
+};
+
+
+/***************************************************************************
+ * Abstract Syntax Tree                                                    *
+ ***************************************************************************/
+
+struct TEnv;        ///< Type-Time Environment
+struct Constraints; ///< Type Constraints
+struct Subst;       ///< Type substitutions
+struct CEnv;        ///< Compile-Time Environment
+
+struct AST;
+extern ostream& operator<<(ostream& out, const AST* ast);
+
+/// Base class for all AST nodes
+struct AST : public Object {
+	AST(Cursor c=Cursor()) : loc(c) {}
+	virtual ~AST() {}
+	virtual bool value() const { return true; }
+	virtual bool operator==(const AST& o) const = 0;
+	virtual bool contains(const AST* child) const { return false; }
+	virtual void constrain(TEnv& tenv, Constraints& c) const {}
+	virtual AST* cps(TEnv& tenv, AST* cont) const;
+	virtual void lift(CEnv& cenv) {}
+	virtual CVal compile(CEnv& cenv) = 0;
+	string str() const { ostringstream ss; ss << this; return ss.str(); }
+	template<typename T> T       to()       { return dynamic_cast<T>(this); }
+	template<typename T> T const to() const { return dynamic_cast<T const>(this); }
+	template<typename T> T as() {
+		T t = dynamic_cast<T>(this);
+		return t ? t : throw Error(loc, "internal error: bad cast");
+	}
+	template<typename T> T const as() const {
+		T const t = dynamic_cast<T const>(this);
+		return t ? t : throw Error(loc, "internal error: bad cast");
+	}
+	Cursor loc;
+};
+
+template<typename T>
+static T* tup(Cursor c, AST* ast, ...)
+{
+	va_list args;
+	va_start(args, ast);
+	T* ret = new T(c, ast, args);
+	va_end(args);
+	return ret;
+}
+
+/// Literal value
+template<typename T>
+struct ALiteral : public AST {
+	ALiteral(T v, Cursor c) : AST(c), val(v) {}
+	bool operator==(const AST& rhs) const {
+		const ALiteral<T>* r = rhs.to<const ALiteral<T>*>();
+		return (r && (val == r->val));
+	}
+	void constrain(TEnv& tenv, Constraints& c) const;
+	CVal compile(CEnv& cenv);
+	const T val;
+};
+
+/// String, e.g. ""a""
+struct AString : public AST, public std::string {
+	AString(Cursor c, const string& s) : AST(c), std::string(s) {}
+	bool operator==(const AST& rhs) const { return this == &rhs; }
+	void constrain(TEnv& tenv, Constraints& c) const;
+	CVal compile(CEnv& cenv) { return NULL; }
+};
+
+/// Symbol, e.g. "a"
+struct ASymbol : public AST {
+	bool operator==(const AST& rhs) const { return this == &rhs; }
+	void constrain(TEnv& tenv, Constraints& c) const;
+	CVal compile(CEnv& cenv);
+	const string cppstr;
+private:
+	friend class PEnv;
+	ASymbol(const string& s, Cursor c) : AST(c), cppstr(s) {}
+};
+
+/// Tuple (heterogeneous sequence of fixed length), e.g. "(a b c)"
+struct ATuple : public AST {
+	ATuple(Cursor c) : AST(c), _len(0), _vec(0) {}
+	ATuple(const ATuple& exp) : AST(exp.loc), _len(exp._len) {
+		_vec = (AST**)malloc(sizeof(AST*) * _len);
+		memcpy(_vec, exp._vec, sizeof(AST*) * _len);
+	}
+	ATuple(Cursor c, AST* ast, va_list args) : AST(c), _len(0), _vec(0) {
+		if (!ast) return;
+		push_back(ast);
+		for (AST* a = va_arg(args, AST*); a; a = va_arg(args, AST*))
+			push_back(a);
+	}
+	~ATuple() { free(_vec); }
+	void push_back(AST* ast) {
+		AST** newvec = (AST**)realloc(_vec, sizeof(AST*) * (_len + 1));
+		newvec[_len++] = ast;
+		_vec = newvec;
+	}
+	const AST* head()  const { assert(_len > 0); return _vec[0]; }
+	AST*       head()        { assert(_len > 0); return _vec[0]; }
+	const AST* last()  const { return _vec[_len - 1]; }
+	AST*       last()        { return _vec[_len - 1]; }
+	size_t     size()  const { return _len; }
+	bool       empty() const { return _len == 0; }
+
+	typedef AST**       iterator;
+	typedef AST* const* const_iterator;
+	const_iterator begin() const { return _vec; }
+	iterator       begin()       { return _vec; }
+	const_iterator end()   const { return _vec + _len; }
+	iterator       end()         { return _vec + _len; }
+
+	bool value() const { return false; }
+	bool operator==(const AST& rhs) const {
+		const ATuple* rt = rhs.to<const ATuple*>();
+		if (!rt || rt->size() != size()) return false;
+		const_iterator l = begin();
+		FOREACHP(const_iterator, r, rt)
+			if (!(*(*l++) == *(*r)))
+				return false;
+		return true;
+	}
+	bool contains(AST* child) const {
+		if (*this == *child) return true;
+		FOREACHP(const_iterator, p, this)
+			if (**p == *child || (*p)->contains(child))
+				return true;
+		return false;
+	}
+	void constrain(TEnv& tenv, Constraints& c) const;
+	void lift(CEnv& cenv) { FOREACHP(iterator, t, this) (*t)->lift(cenv); }
+
+	CVal compile(CEnv& cenv) { throw Error(loc, "tuple compiled"); }
+
+private:
+	size_t _len;
+	AST**  _vec;
+};
+
+/// Type Expression, e.g. "Int", "(Fn (Int Int) Float)"
+struct AType : public ATuple {
+	enum Kind { VAR, PRIM, EXPR, DOTS };
+	AType(ASymbol* s) : ATuple(s->loc), kind(PRIM), id(0) { push_back(s); }
+	AType(Cursor c, unsigned i) : ATuple(c), kind(VAR), id(i) {}
+	AType(Cursor c, Kind k=EXPR) : ATuple(c), kind(k), id(0) {}
+	AType(Cursor c, AST* ast, va_list args) : ATuple(c, ast, args), kind(EXPR), id(0) {}
+	AType(const AType& copy) : ATuple(copy), kind(copy.kind), id(copy.id) {}
+	CVal compile(CEnv& cenv) { return NULL; }
+	const ATuple* prot() const { assert(kind == EXPR); return (*(begin() + 1))->to<const ATuple*>(); }
+	ATuple*       prot()       { assert(kind == EXPR); return (*(begin() + 1))->to<ATuple*>(); }
+	bool concrete() const {
+		switch (kind) {
+		case VAR:  return false;
+		case PRIM: return head()->str() != "Nothing";
+		case EXPR:
+			FOREACHP(const_iterator, t, this) {
+				AType* kid = (*t)->to<AType*>();
+				if (kid && !kid->concrete())
+					return false;
+			}
+		}
+		return true;
+	}
+	bool operator==(const AST& rhs) const {
+		const AType* rt = rhs.to<const AType*>();
+		if (!rt || kind != rt->kind)
+			return false;
+		else
+			switch (kind) {
+			case VAR:  return id == rt->id;
+			case PRIM: return head()->str() == rt->head()->str();
+			case EXPR: return ATuple::operator==(rhs);
+			}
+		return false; // never reached
+	}
+	Kind     kind;
+	unsigned id;
+};
+
+/// Type substitution
+struct Subst : public list< pair<const AType*,AType*> > {
+	Subst(AType* s=0, AType* t=0) { if (s && t) { assert(s != t); push_back(make_pair(s, t)); } }
+	static Subst compose(const Subst& delta, const Subst& gamma);
+	void add(const AType* from, AType* to) { push_back(make_pair(from, to)); }
+	const_iterator find(const AType* t) const {
+		for (const_iterator j = begin(); j != end(); ++j)
+			if (*j->first == *t)
+				return j;
+		return end();
+	}
+	AType* apply(const AType* in) const {
+		if (in->kind == AType::EXPR) {
+			AType* out = tup<AType>(in->loc, NULL);
+			for (ATuple::const_iterator i = in->begin(); i != in->end(); ++i)
+				out->push_back(apply((*i)->as<AType*>()));
+			return out;
+		} else {
+			const_iterator i = find(in);
+			if (i != end()) {
+				AType* out = i->second->as<AType*>();
+				if (out->kind == AType::EXPR && !out->concrete())
+					out = apply(out->as<AType*>());
+				return out;
+			} else {
+				return new AType(*in);
+			}
+		}
+	}
+};
+
+inline ostream& operator<<(ostream& out, const Subst& s) {
+	for (Subst::const_iterator i = s.begin(); i != s.end(); ++i)
+		out << i->first << " => " << i->second << endl;
+	return out;
+}
+
+/// Fn (first-class function with captured lexical bindings)
+struct AFn : public ATuple {
+	AFn(Cursor c, AST* ast, va_list args) : ATuple(c, ast, args) {}
+	bool operator==(const AST& rhs) const { return this == &rhs; }
+	void constrain(TEnv& tenv, Constraints& c) const;
+	AST* cps(TEnv& tenv, AST* cont) const;
+	void lift(CEnv& cenv);
+	CVal compile(CEnv& cenv);
+	const ATuple* prot() const { return (*(begin() + 1))->to<const ATuple*>(); }
+	ATuple*       prot()       { return (*(begin() + 1))->to<ATuple*>(); }
+	/// System level implementations of this (polymorphic) fn
+	struct Impls : public list< pair<AType*, CFunc> > {
+		CFunc find(AType* type) const {
+			for (const_iterator f = begin(); f != end(); ++f)
+				if (*f->first == *type)
+					return f->second;
+			return NULL;
+		}
+	};
+	Impls  impls;
+	string name;
+};
+
+/// Function call/application, e.g. "(func arg1 arg2)"
+struct ACall : public ATuple {
+	ACall(const ATuple* exp) : ATuple(*exp) {}
+	ACall(Cursor c, AST* ast, va_list args) : ATuple(c, ast, args) {}
+	void constrain(TEnv& tenv, Constraints& c) const;
+	AST* cps(TEnv& tenv, AST* cont) const;
+	void lift(CEnv& cenv);
+	CVal compile(CEnv& cenv);
+};
+
+/// Definition special form, e.g. "(def x 2)"
+struct ADef : public ACall {
+	ADef(const ATuple* exp) : ACall(exp) {}
+	ADef(Cursor c, AST* ast, va_list args) : ACall(c, ast, args) {}
+	const ASymbol* sym() const {
+		const AST*     name = *(begin() + 1);
+		const ASymbol* sym  = name->to<const ASymbol*>();
+		if (!sym) {
+			const ATuple* tup = name->to<const ATuple*>();
+			if (tup && !tup->empty())
+				return tup->head()->to<const ASymbol*>();
+		}
+		return sym;
+	}
+	const AST* body() const { return *(begin() + 2); }
+	AST*       body()       { return *(begin() + 2); }
+	void constrain(TEnv& tenv, Constraints& c) const;
+	AST* cps(TEnv& tenv, AST* cont) const;
+	void lift(CEnv& cenv);
+	CVal compile(CEnv& cenv);
+};
+
+/// Conditional special form, e.g. "(if cond thenexp elseexp)"
+struct AIf : public ACall {
+	AIf(const ATuple* exp) : ACall(exp) {}
+	AIf(Cursor c, AST* ast, va_list args) : ACall(c, ast, args) {}
+	void constrain(TEnv& tenv, Constraints& c) const;
+	AST* cps(TEnv& tenv, AST* cont) const;
+	CVal compile(CEnv& cenv);
+};
+
+struct ACons : public ACall {
+	ACons(const ATuple* exp) : ACall(exp) {}
+	void constrain(TEnv& tenv, Constraints& c) const;
+	CVal compile(CEnv& cenv);
+};
+
+struct ADot : public ACall {
+	ADot(const ATuple* exp) : ACall(exp) {}
+	void constrain(TEnv& tenv, Constraints& c) const;
+	void lift(CEnv& cenv);
+	CVal compile(CEnv& cenv);
+};
+
+/// Primitive (builtin arithmetic function), e.g. "(+ 2 3)"
+struct APrimitive : public ACall {
+	APrimitive(const ATuple* exp) : ACall(exp) {}
+	bool value() const {
+		ATuple::const_iterator i = begin();
+		for (++i; i != end(); ++i)
+			if (!(*i)->value())
+				return false;;
+		return true;
+	}
+	void constrain(TEnv& tenv, Constraints& c) const;
+	AST* cps(TEnv& tenv, AST* cont) const;
+	CVal compile(CEnv& cenv);
+};
+
+
+/***************************************************************************
+ * Parser: S-Expressions (SExp) -> AST Nodes (AST)                         *
+ ***************************************************************************/
+
+/// Parse Time Environment (really just a symbol table)
+struct PEnv : private map<const string, ASymbol*> {
+	PEnv() : symID(0) {}
+	typedef AST* (*PF)(PEnv&, const AST*, void*); ///< Parse Function
+	typedef AST* (*MF)(PEnv&, const AST*); ///< Macro Function
+	struct Handler { Handler(PF f, void* a=0) : func(f), arg(a) {} PF func; void* arg; };
+	map<const string, Handler> aHandlers; ///< Atom parse functions
+	map<const string, Handler> lHandlers; ///< List parse functions
+	map<const string, MF>      macros; ///< Macro functions
+	void reg(bool list, const string& s, const Handler& h) {
+		(list ? lHandlers : aHandlers).insert(make_pair(sym(s)->str(), h));
+	}
+	const Handler* handler(bool list, const string& s) const {
+		const map<const string, Handler>& handlers = list ? lHandlers : aHandlers;
+		map<string, Handler>::const_iterator i = handlers.find(s);
+		return (i != handlers.end()) ? &i->second : NULL;
+	}
+	void defmac(const string& s, const MF f) {
+		macros.insert(make_pair(s, f));
+	}
+	MF mac(const AString& s) const {
+		map<string, MF>::const_iterator i = macros.find(s);
+		return (i != macros.end()) ? i->second : NULL;
+	}
+	string gensymstr(const char* s="_") { return (format("%s%d") % s % symID++).str(); }
+	ASymbol* gensym(const char* s="_") { return sym(gensymstr(s)); }
+	ASymbol* sym(const string& s, Cursor c=Cursor()) {
+		const const_iterator i = find(s);
+		if (i != end()) {
+			return i->second;
+		} else {
+			ASymbol* sym = new ASymbol(s, c);
+			insert(make_pair(s, sym));
+			return sym;
+		}
+	}
+	ATuple* parseTuple(const ATuple* e) {
+		ATuple* ret = new ATuple(e->loc);
+		FOREACHP(ATuple::const_iterator, i, e)
+			ret->push_back(parse(*i));
+		return ret;
+	}
+	AST* parse(const AST* exp) {
+		const ATuple* tup = exp->to<const ATuple*>();
+		if (tup) {
+			if (tup->empty()) throw Error(exp->loc, "call to empty list");
+			if (!tup->head()->to<const ATuple*>()) {
+				MF mf = mac(*tup->head()->to<const AString*>());
+				const AST*    expanded     = (mf ? mf(*this, exp) : exp);
+				const ATuple* expanded_tup = expanded->to<const ATuple*>();
+				const PEnv::Handler* h = handler(true, *expanded_tup->head()->to<const AString*>());
+				if (h)
+					return h->func(*this, expanded, h->arg);
+			}
+			ATuple* parsed_tup = parseTuple(tup);
+			return new ACall(parsed_tup); // Parse as regular call
+		}
+		const AString* str = exp->to<const AString*>();
+		assert(str);
+		if (isdigit((*str)[0])) {
+			const std::string& s = *str;
+			if (s.find('.') == string::npos)
+				return new ALiteral<int32_t>(strtol(s.c_str(), NULL, 10), exp->loc);
+			else
+				return new ALiteral<float>(strtod(s.c_str(), NULL), exp->loc);
+		} else if ((*str)[0] == '\"') {
+			return new AString(exp->loc, str->substr(1, str->length() - 2));
+		} else {
+			const PEnv::Handler* h = handler(false, *str);
+			if (h)
+				return h->func(*this, exp, h->arg);
+		}
+		return sym(*exp->to<const AString*>(), exp->loc);
+	}
+	unsigned symID;
+};
+
+
+/***************************************************************************
+ * Typing                                                                  *
+ ***************************************************************************/
+
+/// Type constraint
+struct Constraint : public pair<AType*,AType*> {
+	Constraint(AType* a, AType* b, Cursor c) : pair<AType*,AType*>(a, b), loc(c) {}
+	Cursor loc;
+};
+
+/// Type constraint set
+struct Constraints : public list<Constraint> {
+	void constrain(TEnv& tenv, const AST* o, AType* t);
+	void replace(AType* s, AType* t);
+};
+
+inline ostream& operator<<(ostream& out, const Constraints& c) {
+	for (Constraints::const_iterator i = c.begin(); i != c.end(); ++i)
+		out << i->first << " : " << i->second << endl;
+	return out;
+}
+
+/// Type-Time Environment
+struct TEnv : public Env<const ASymbol*, AType*> {
+	TEnv(PEnv& p)
+		: penv(p)
+		, varID(1)
+		, Fn(new AType(penv.sym("Fn")))
+		, Tup(new AType(penv.sym("Tup")))
+	{
+		Object::pool.addRoot(Fn);
+	}
+	AType* fresh(const ASymbol* sym) {
+		return def(sym, new AType(sym->loc, varID++));
+	}
+	AType* var(const AST* ast=0) {
+		if (!ast)
+			return new AType(Cursor(), varID++);
+
+		const ASymbol* sym = ast->to<const ASymbol*>();
+		if (sym)
+			return *ref(sym);
+
+		Vars::iterator v = vars.find(ast);
+		if (v != vars.end())
+			return v->second;
+
+		return (vars[ast] = new AType(ast->loc, varID++));
+	}
+	AType* named(const string& name) {
+		return *ref(penv.sym(name));
+	}
+	static Subst buildSubst(AType* fnT, const AType& argsT);
+
+	typedef map<const AST*, AType*> Vars;
+
+	Vars     vars;
+	PEnv&    penv;
+	unsigned varID;
+
+	AType* Fn;
+	AType* Tup;
+};
+
+Subst unify(const Constraints& c);
+
+
+/***************************************************************************
+ * Code Generation                                                         *
+ ***************************************************************************/
+
+/// Compiler backend
+struct Engine {
+	virtual ~Engine() {}
+
+	virtual CFunc startFunction(
+			CEnv&                cenv,
+			const std::string&   name,
+			const AType*         retT,
+			const ATuple&        argsT,
+			const vector<string> argNames=vector<string>()) = 0;
+
+	virtual void  finishFunction(CEnv& cenv, CFunc f, const AType* retT, CVal ret) = 0;
+	virtual void  eraseFunction(CEnv& cenv, CFunc f)                               = 0;
+	virtual CFunc compileFunction(CEnv& cenv, AFn* fn, const AType& argsT)         = 0;
+	virtual CVal  compileTup(CEnv& cenv, const AType* t, const vector<CVal>& f)    = 0;
+	virtual CVal  compileDot(CEnv& cenv, CVal tup, int32_t index)                  = 0;
+	virtual CVal  compileLiteral(CEnv& cenv, AST* lit)                             = 0;
+	virtual CVal  compileCall(CEnv& cenv, CFunc f, const vector<CVal>& args)       = 0;
+	virtual CVal  compilePrimitive(CEnv& cenv, APrimitive* prim)                   = 0;
+	virtual CVal  compileIf(CEnv& cenv, AIf* aif)                                  = 0;
+	virtual CVal  compileGlobal(CEnv& cenv, AType* t, const string& sym, CVal val) = 0;
+	virtual CVal  getGlobal(CEnv& cenv, CVal val)                                  = 0;
+	virtual void  writeModule(CEnv& cenv, std::ostream& os)                        = 0;
+
+	virtual const string call(CEnv& cenv, CFunc f, AType* retT) = 0;
+};
+
+Engine* resp_new_llvm_engine();
+Engine* resp_new_c_engine();
+
+/// Compile-Time Environment
+struct CEnv {
+	CEnv(PEnv& p, TEnv& t, Engine* e, ostream& os=std::cout, ostream& es=std::cerr)
+		: out(os), err(es), penv(p), tenv(t), _engine(e)
+	{}
+
+	~CEnv() { Object::pool.collect(GC::Roots()); }
+
+	typedef Env<const ASymbol*, CVal> Vals;
+
+	Engine* engine() { return _engine; }
+	void    push() { code.push(); tenv.push(); vals.push(); }
+	void    pop()  { code.pop(); tenv.pop();  vals.pop();  }
+	void    lock(AST* ast) { Object::pool.addRoot(ast); Object::pool.addRoot(type(ast)); }
+	AType*  type(AST* ast, const Subst& subst = Subst()) const {
+		ASymbol* sym = ast->to<ASymbol*>();
+		if (sym)
+			return *tenv.ref(sym);
+		assert(tenv.vars[ast]);
+		return tsubst.apply(subst.apply(tenv.vars[ast]))->to<AType*>();
+	}
+	void def(const ASymbol* sym, AST* c, AType* t, CVal v) {
+		code.def(sym, c);
+		tenv.def(sym, t);
+		vals.def(sym, v);
+	}
+	AST* resolve(AST* ast) {
+		const ASymbol* sym = ast->to<const ASymbol*>();
+		AST**          rec = code.ref(sym);
+		return rec ? *rec : ast;
+	}
+
+	ostream& out;
+	ostream& err;
+	PEnv&    penv;
+	TEnv&    tenv;
+	Vals     vals;
+	Subst    tsubst;
+
+	Env<const ASymbol*, AST*> code;
+
+	map<string,string> args;
+
+private:
+	Engine* _engine;
+};
+
+
+/***************************************************************************
+ * EVAL/REPL/MAIN                                                          *
+ ***************************************************************************/
+
+void pprint(std::ostream& out, const AST* ast);
+void initLang(PEnv& penv, TEnv& tenv);
+int  eval(CEnv& cenv, const string& name, istream& is, bool execute);
+int  repl(CEnv& cenv);
+
+#endif // RESP_HPP