From 8675beae4f7a8415fc2e88451da95dc068719194 Mon Sep 17 00:00:00 2001
From: David Robillard <d@drobilla.net>
Date: Tue, 13 Apr 2010 02:28:56 +0000
Subject: Restructure as a source translation based compiler. Implement support
 for closures (via lambda lifting phase).

git-svn-id: http://svn.drobilla.net/resp/resp@254 ad02d1e2-f140-0410-9f75-f8b11f17cedd
---
 src/unify.cpp | 49 +++++++++++++++++++++++++++++++------------------
 1 file changed, 31 insertions(+), 18 deletions(-)

(limited to 'src/unify.cpp')

diff --git a/src/unify.cpp b/src/unify.cpp
index 93dd78b..1b25861 100644
--- a/src/unify.cpp
+++ b/src/unify.cpp
@@ -26,7 +26,7 @@
  * with a specific set of argument types
  */
 Subst
-TEnv::buildSubst(AType* genericT, const AType& argsT)
+TEnv::buildSubst(const AType* genericT, const AType& argsT)
 {
 	Subst subst;
 
@@ -56,7 +56,7 @@ TEnv::buildSubst(AType* genericT, const AType& argsT)
 }
 
 void
-Constraints::constrain(TEnv& tenv, const AST* o, AType* t)
+Constraints::constrain(TEnv& tenv, const AST* o, const AType* t)
 {
 	assert(o);
 	assert(t);
@@ -64,15 +64,27 @@ Constraints::constrain(TEnv& tenv, const AST* o, AType* t)
 	push_back(Constraint(tenv.var(o), t, o->loc));
 }
 
-static void
-substitute(ATuple* tup, const AST* from, AST* to)
+template<typename T, typename E>
+static const T*
+substitute(const T* tup, const E* from, const E* to)
 {
-	if (!tup) return;
-	FOREACHP(ATuple::iterator, i, tup)
-		if (**i == *from)
-			*i = to;
-		else if (*i != to)
-			substitute((*i)->to<ATuple*>(), from, to);
+	if (!tup) return NULL;
+	T* ret = new T(*tup);
+	typename T::iterator ri = ret->begin();
+	FOREACHP(typename T::const_iterator, i, tup) {
+		if (**i == *from) {
+			*ri++ = const_cast<E*>(to);
+		} else if (static_cast<const E*>(*i) != static_cast<const E*>(to)) {
+			const T* subTup = dynamic_cast<const T*>(*i);
+			if (subTup)
+				*ri++ = const_cast<E*>(substitute(subTup, from, to));
+			else
+				*ri++ = *i;
+		} else {
+			++ri;
+		}
+	}
+	return ret;
 }
 
 /// Compose two substitutions (TAPL 22.1.1)
@@ -92,15 +104,16 @@ Subst::compose(const Subst& delta, const Subst& gamma)
 }
 
 /// Replace all occurrences of @a s with @a t
-Constraints&
-Constraints::replace(AType* s, AType* t)
+Constraints
+Constraints::replace(const AType* s, const AType* t)
 {
+	Constraints cp(*this);
 	for (Constraints::iterator c = begin(); c != end();) {
 		Constraints::iterator next = c; ++next;
 		if (*c->first  == *s) c->first  = t;
 		if (*c->second == *s) c->second = t;
-		substitute(c->first, s, t);
-		substitute(c->second, s, t);
+		c->first = substitute(c->first, s, t);
+		c->second = substitute(c->second, s, t);
 		c = next;
 	}
 	return *this;
@@ -114,8 +127,8 @@ unify(const Constraints& constraints)
 		return Subst();
 
 	Constraints::const_iterator i  = constraints.begin();
-	AType*                      s  = i->first;
-	AType*                      t  = i->second;
+	const AType*                s  = i->first;
+	const AType*                t  = i->second;
 	Constraints                 cp(++i, constraints.end());
 
 	if (*s == *t) {
@@ -125,8 +138,8 @@ unify(const Constraints& constraints)
 	} else if (t->kind == AType::VAR && !s->contains(t)) {
 		return Subst::compose(unify(cp.replace(t, s)), Subst(t, s));
 	} else if (s->kind == AType::EXPR && t->kind == AType::EXPR) {
-		AType::iterator si = s->begin() + 1;
-		AType::iterator ti = t->begin() + 1;
+		AType::const_iterator si = s->begin() + 1;
+		AType::const_iterator ti = t->begin() + 1;
 		for (; si != s->end() && ti != t->end(); ++si, ++ti) {
 			AType* st = (*si)->as<AType*>();
 			AType* tt = (*ti)->as<AType*>();
-- 
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