diff --git a/js-assembler/get-runtime.rkt b/js-assembler/get-runtime.rkt
index a60412e..698a2a6 100644
--- a/js-assembler/get-runtime.rkt
+++ b/js-assembler/get-runtime.rkt
@@ -37,6 +37,8 @@
 (define-runtime-path baselib.js "runtime-src/baselib.js")
 (define-runtime-path baselib_unionfind.js "runtime-src/baselib_unionfind.js")
 (define-runtime-path baselib_equality.js "runtime-src/baselib_equality.js")
+(define-runtime-path baselib_lists.js "runtime-src/baselib_lists.js")
+(define-runtime-path baselib_vectors.js "runtime-src/baselib_vectors.js")
 (define-runtime-path baselib_hash.js "runtime-src/baselib_hash.js")
 (define-runtime-path baselib_symbol.js "runtime-src/baselib_symbol.js")
 (define-runtime-path baselib_structs.js "runtime-src/baselib_structs.js")
@@ -79,16 +81,20 @@
                     baselib.js
                     baselib_unionfind.js
                     baselib_equality.js
-                    baselib_hash.js
                     baselib_format.js
+                    
+                    baselib_lists.js
+                    baselib_vectors.js
+                    baselib_chars.js
                     baselib_symbol.js
+                    baselib_strings.js
+                    baselib_bytes.js                    
+                    baselib_hash.js
+
                     baselib_structs.js
                     baselib_arity.js
                     baselib_inspectors.js
                     baselib_exceptions.js
-                    baselib_chars.js
-                    baselib_strings.js
-                    baselib_bytes.js
                     baselib_readergraph.js
 
                     link.js
diff --git a/js-assembler/runtime-src/baselib_arity.js b/js-assembler/runtime-src/baselib_arity.js
index 2d16b2a..d528aab 100644
--- a/js-assembler/runtime-src/baselib_arity.js
+++ b/js-assembler/runtime-src/baselib_arity.js
@@ -35,7 +35,7 @@
 	} else if (isArityAtLeast(arity)) {
 	    return n >= arityAtLeastValue(arity);
 	} else {
-	    while (arity !== plt.types.EMPTY) {
+	    while (arity !== plt.baselib.lists.EMPTY) {
 		if (typeof(arity.first) === 'number') {
 		    if (arity.first === n) { return true; }
 		} else if (isArityAtLeast(arity)) {
diff --git a/js-assembler/runtime-src/baselib_lists.js b/js-assembler/runtime-src/baselib_lists.js
new file mode 100644
index 0000000..2b4ba37
--- /dev/null
+++ b/js-assembler/runtime-src/baselib_lists.js
@@ -0,0 +1,159 @@
+// list structures (pairs, empty)
+(function(baselib) {
+    var exports = {};
+    baselib.lists = exports;
+
+    
+
+
+    
+    Empty = function() {
+    };
+    Empty.EMPTY = new Empty();
+
+
+    Empty.prototype.equals = function(other, aUnionFind) {
+        return other instanceof Empty;
+    };
+
+    Empty.prototype.reverse = function() {
+        return this;
+    };
+
+    Empty.prototype.toWrittenString = function(cache) { return "empty"; };
+    Empty.prototype.toDisplayedString = function(cache) { return "empty"; };
+    Empty.prototype.toString = function(cache) { return "()"; };
+
+    
+    // Empty.append: (listof X) -> (listof X)
+    Empty.prototype.append = function(b){
+        return b;
+    };
+    
+
+
+
+    //////////////////////////////////////////////////////////////////////
+
+    // Cons Pairs
+
+    var Cons = function(f, r) {
+        this.first = f;
+        this.rest = r;
+    };
+
+    Cons.prototype.reverse = function() {
+        var lst = this;
+        var ret = Empty.EMPTY;
+        while (!isEmpty(lst)){
+	    ret = Cons.makeInstance(lst.first, ret);
+	    lst = lst.rest;
+        }
+        return ret;
+    };
+    
+    Cons.makeInstance = function(f, r) {
+        return new Cons(f, r);
+    };
+
+    // FIXME: can we reduce the recursion on this?
+    Cons.prototype.equals = function(other, aUnionFind) {
+        if (! (other instanceof Cons)) {
+	    return false;
+        }
+        return (plt.baselib.equality.equals(this.first, other.first, aUnionFind) &&
+	        plt.baselib.equality.equals(this.rest, other.rest, aUnionFind));
+    };
+    
+
+    
+
+    // Cons.append: (listof X) -> (listof X)
+    Cons.prototype.append = function(b){
+        if (b === Empty.EMPTY)
+	    return this;
+        var ret = b;
+        var lst = this.reverse();
+        while ( !isEmpty(lst) ) {
+	    ret = Cons.makeInstance(lst.first, ret);
+	    lst = lst.rest;
+        }
+	
+        return ret;
+    };
+    
+
+    Cons.prototype.toWrittenString = function(cache) {
+        cache.put(this, true);
+        var texts = [];
+        var p = this;
+        while ( p instanceof Cons ) {
+	    texts.push(plt.baselib.format.toWrittenString(p.first, cache));
+	    p = p.rest;
+	    if (typeof(p) === 'object' && cache.containsKey(p)) {
+	        break;
+	    }
+        }
+        if ( p !== Empty.EMPTY ) {
+	    texts.push('.');
+	    texts.push(plt.baselib.format.toWrittenString(p, cache));
+        }
+        return "(" + texts.join(" ") + ")";
+    };
+
+    Cons.prototype.toString = Cons.prototype.toWrittenString;
+
+    Cons.prototype.toDisplayedString = function(cache) {
+        cache.put(this, true);
+        var texts = [];
+        var p = this;
+        while ( p instanceof Cons ) {
+	    texts.push(plt.baselib.format.toDisplayedString(p.first, cache));
+	    p = p.rest;
+	    if (typeof(p) === 'object' && cache.containsKey(p)) {
+	        break;
+	    }
+        }
+        if ( p !== Empty.EMPTY ) {
+	    texts.push('.');
+	    texts.push(plt.baselib.format.toDisplayedString(p, cache));
+        }
+        return "(" + texts.join(" ") + ")";
+    };
+
+
+
+    Cons.prototype.toDomNode = function(cache) {
+        cache.put(this, true);
+        var node = document.createElement("span");
+        node.appendChild(document.createTextNode("("));
+        var p = this;
+        while ( p instanceof Cons ) {
+	    appendChild(node, plt.baselib.format.toDomNode(p.first, cache));
+	    p = p.rest;
+	    if ( p !== Empty.EMPTY ) {
+	        appendChild(node, document.createTextNode(" "));
+	    }
+	    if (typeof(p) === 'object' && cache.containsKey(p)) {
+	        break;
+	    }
+        }
+        if ( p !== Empty.EMPTY ) {
+	    appendChild(node, document.createTextNode("."));
+	    appendChild(node, document.createTextNode(" "));
+	    appendChild(node, plt.baselib.format.toDomNode(p, cache));
+        }
+
+        node.appendChild(document.createTextNode(")"));
+        return node;
+    };
+
+
+
+    exports.EMPTY = Empty.EMPTY;
+    exports.Empty = Empty;
+    exports.Cons = Cons;
+
+
+
+})(this['plt'].baselib);
\ No newline at end of file
diff --git a/js-assembler/runtime-src/baselib_vectors.js b/js-assembler/runtime-src/baselib_vectors.js
new file mode 100644
index 0000000..4cb5a00
--- /dev/null
+++ b/js-assembler/runtime-src/baselib_vectors.js
@@ -0,0 +1,99 @@
+// vectors
+(function(baselib) {
+    var exports = {};
+    baselib.vectors = exports;
+
+
+
+    Vector = function(n, initialElements) {
+        this.elts = new Array(n);
+        if (initialElements) {
+	    for (var i = 0; i < n; i++) {
+	        this.elts[i] = initialElements[i];
+	    }
+        } else {
+	    for (var i = 0; i < n; i++) {
+	        this.elts[i] = undefined;
+	    }
+        }
+        this.mutable = true;
+    };
+
+    Vector.makeInstance = function(n, elts) {
+        return new Vector(n, elts);
+    }
+
+    Vector.prototype.length = function() {
+	return this.elts.length;
+    };
+
+    Vector.prototype.ref = function(k) {
+        return this.elts[k];
+    };
+
+    Vector.prototype.set = function(k, v) {
+        this.elts[k] = v;
+    };
+
+    Vector.prototype.equals = function(other, aUnionFind) {
+        if (other != null && other != undefined && other instanceof Vector) {
+	    if (other.length() != this.length()) {
+	        return false
+	    }
+	    for (var i = 0; i <  this.length(); i++) {
+	        if (! plt.baselib.equality.equals(this.elts[i], other.elts[i], aUnionFind)) {
+		    return false;
+	        }
+	    }
+	    return true;
+        } else {
+	    return false;
+        }
+    };
+
+    Vector.prototype.toList = function() {
+        var ret = plt.baselib.lists.EMPTY;
+        for (var i = this.length() - 1; i >= 0; i--) {
+	    ret = plt.baselib.lists.Cons.makeInstance(this.elts[i], ret);	    
+        }	
+        return ret;
+    };
+
+    Vector.prototype.toWrittenString = function(cache) {
+        cache.put(this, true);
+        var texts = [];
+        for (var i = 0; i < this.length(); i++) {
+	    texts.push(plt.baselib.format.toWrittenString(this.ref(i), cache));
+        }
+        return "#(" + texts.join(" ") + ")";
+    };
+
+    Vector.prototype.toDisplayedString = function(cache) {
+        cache.put(this, true);
+        var texts = [];
+        for (var i = 0; i < this.length(); i++) {
+	    texts.push(plt.baselib.format.toDisplayedString(this.ref(i), cache));
+        }
+        return "#(" + texts.join(" ") + ")";
+    };
+
+    Vector.prototype.toDomNode = function(cache) {
+        cache.put(this, true);
+        var node = document.createElement("span");
+        node.appendChild(document.createTextNode("#("));
+        for (var i = 0; i < this.length(); i++) {
+	    appendChild(node,
+		        plt.baselib.format.toDomNode(this.ref(i), cache));
+	    if (i !== this.length()-1) {
+	        appendChild(node, document.createTextNode(" "));
+	    }
+        }
+        node.appendChild(document.createTextNode(")"));
+        return node;
+    };
+
+
+
+    exports.Vector = Vector;
+
+})(this['plt'].baselib);
\ No newline at end of file
diff --git a/js-assembler/runtime-src/types.js b/js-assembler/runtime-src/types.js
index 8018e44..518c81c 100644
--- a/js-assembler/runtime-src/types.js
+++ b/js-assembler/runtime-src/types.js
@@ -39,6 +39,8 @@ if (! this['plt']) { this['plt'] = {}; }
 
 
     var Symbol = plt.baselib.Symbol;
+    var Empty = plt.baselib.lists.Empty;
+    var Cons = plt.baselib.lists.Cons;
 
     //////////////////////////////////////////////////////////////////////
 
@@ -238,150 +240,6 @@ if (! this['plt']) { this['plt'] = {}; }
 
     
     
-    
-    Empty = function() {
-    };
-    Empty.EMPTY = new Empty();
-
-
-    Empty.prototype.equals = function(other, aUnionFind) {
-        return other instanceof Empty;
-    };
-
-    Empty.prototype.reverse = function() {
-        return this;
-    };
-
-    Empty.prototype.toWrittenString = function(cache) { return "empty"; };
-    Empty.prototype.toDisplayedString = function(cache) { return "empty"; };
-    Empty.prototype.toString = function(cache) { return "()"; };
-
-
-    
-    // Empty.append: (listof X) -> (listof X)
-    Empty.prototype.append = function(b){
-        return b;
-    };
-    
-
-
-
-    //////////////////////////////////////////////////////////////////////
-
-    // Cons Pairs
-
-    var Cons = function(f, r) {
-        this.first = f;
-        this.rest = r;
-    };
-
-    Cons.prototype.reverse = function() {
-        var lst = this;
-        var ret = Empty.EMPTY;
-        while (!isEmpty(lst)){
-	    ret = Cons.makeInstance(lst.first, ret);
-	    lst = lst.rest;
-        }
-        return ret;
-    };
-    
-    Cons.makeInstance = function(f, r) {
-        return new Cons(f, r);
-    };
-
-    // FIXME: can we reduce the recursion on this?
-    Cons.prototype.equals = function(other, aUnionFind) {
-        if (! (other instanceof Cons)) {
-	    return false;
-        }
-        return (equals(this.first, other.first, aUnionFind) &&
-	        equals(this.rest, other.rest, aUnionFind));
-    };
-    
-
-    
-
-    // Cons.append: (listof X) -> (listof X)
-    Cons.prototype.append = function(b){
-        if (b === Empty.EMPTY)
-	    return this;
-        var ret = b;
-        var lst = this.reverse();
-        while ( !isEmpty(lst) ) {
-	    ret = Cons.makeInstance(lst.first, ret);
-	    lst = lst.rest;
-        }
-	
-        return ret;
-    };
-    
-
-    Cons.prototype.toWrittenString = function(cache) {
-        cache.put(this, true);
-        var texts = [];
-        var p = this;
-        while ( p instanceof Cons ) {
-	    texts.push(toWrittenString(p.first, cache));
-	    p = p.rest;
-	    if (typeof(p) === 'object' && cache.containsKey(p)) {
-	        break;
-	    }
-        }
-        if ( p !== Empty.EMPTY ) {
-	    texts.push('.');
-	    texts.push(toWrittenString(p, cache));
-        }
-        return "(" + texts.join(" ") + ")";
-    };
-
-    Cons.prototype.toString = Cons.prototype.toWrittenString;
-
-    Cons.prototype.toDisplayedString = function(cache) {
-        cache.put(this, true);
-        var texts = [];
-        var p = this;
-        while ( p instanceof Cons ) {
-	    texts.push(toDisplayedString(p.first, cache));
-	    p = p.rest;
-	    if (typeof(p) === 'object' && cache.containsKey(p)) {
-	        break;
-	    }
-        }
-        if ( p !== Empty.EMPTY ) {
-	    texts.push('.');
-	    texts.push(toDisplayedString(p, cache));
-        }
-        return "(" + texts.join(" ") + ")";
-    };
-
-
-
-    Cons.prototype.toDomNode = function(cache) {
-        cache.put(this, true);
-        var node = document.createElement("span");
-        node.appendChild(document.createTextNode("("));
-        var p = this;
-        while ( p instanceof Cons ) {
-	    appendChild(node, toDomNode(p.first, cache));
-	    p = p.rest;
-	    if ( p !== Empty.EMPTY ) {
-	        appendChild(node, document.createTextNode(" "));
-	    }
-	    if (typeof(p) === 'object' && cache.containsKey(p)) {
-	        break;
-	    }
-        }
-        if ( p !== Empty.EMPTY ) {
-	    appendChild(node, document.createTextNode("."));
-	    appendChild(node, document.createTextNode(" "));
-	    appendChild(node, toDomNode(p, cache));
-        }
-
-        node.appendChild(document.createTextNode(")"));
-        return node;
-    };
-
-
     // isList: Any -> Boolean
     // Returns true if x is a list (a chain of pairs terminated by EMPTY).
     var isList = function(x) { 
@@ -400,89 +258,6 @@ if (! this['plt']) { this['plt'] = {}; }
 
     //////////////////////////////////////////////////////////////////////
 
-    Vector = function(n, initialElements) {
-        this.elts = new Array(n);
-        if (initialElements) {
-	    for (var i = 0; i < n; i++) {
-	        this.elts[i] = initialElements[i];
-	    }
-        } else {
-	    for (var i = 0; i < n; i++) {
-	        this.elts[i] = undefined;
-	    }
-        }
-        this.mutable = true;
-    };
-    Vector.makeInstance = function(n, elts) {
-        return new Vector(n, elts);
-    }
-    Vector.prototype.length = function() {
-	return this.elts.length;
-    };
-    Vector.prototype.ref = function(k) {
-        return this.elts[k];
-    };
-    Vector.prototype.set = function(k, v) {
-        this.elts[k] = v;
-    };
-
-    Vector.prototype.equals = function(other, aUnionFind) {
-        if (other != null && other != undefined && other instanceof Vector) {
-	    if (other.length() != this.length()) {
-	        return false
-	    }
-	    for (var i = 0; i <  this.length(); i++) {
-	        if (! equals(this.elts[i], other.elts[i], aUnionFind)) {
-		    return false;
-	        }
-	    }
-	    return true;
-        } else {
-	    return false;
-        }
-    };
-
-    Vector.prototype.toList = function() {
-        var ret = Empty.EMPTY;
-        for (var i = this.length() - 1; i >= 0; i--) {
-	    ret = Cons.makeInstance(this.elts[i], ret);	    
-        }	
-        return ret;
-    };
-
-    Vector.prototype.toWrittenString = function(cache) {
-        cache.put(this, true);
-        var texts = [];
-        for (var i = 0; i < this.length(); i++) {
-	    texts.push(toWrittenString(this.ref(i), cache));
-        }
-        return "#(" + texts.join(" ") + ")";
-    };
-
-    Vector.prototype.toDisplayedString = function(cache) {
-        cache.put(this, true);
-        var texts = [];
-        for (var i = 0; i < this.length(); i++) {
-	    texts.push(toDisplayedString(this.ref(i), cache));
-        }
-        return "#(" + texts.join(" ") + ")";
-    };
-
-    Vector.prototype.toDomNode = function(cache) {
-        cache.put(this, true);
-        var node = document.createElement("span");
-        node.appendChild(document.createTextNode("#("));
-        for (var i = 0; i < this.length(); i++) {
-	    appendChild(node,
-		        toDomNode(this.ref(i), cache));
-	    if (i !== this.length()-1) {
-	        appendChild(node, document.createTextNode(" "));
-	    }
-        }
-        node.appendChild(document.createTextNode(")"));
-        return node;
-    };
-
 
     //////////////////////////////////////////////////////////////////////
 
@@ -1003,7 +778,7 @@ if (! this['plt']) { this['plt'] = {}; }
     types.bytes = function(x, mutable) { return new plt.baselib.bytes.Bytes(x, mutable); };
     types.bytesImmutable = function(x) { return new plt.baselib.bytes.Bytes(x, false); };
     types.keyword = function(k) { return new Keyword(k); };
-    types.pair = function(x, y) { return Cons.makeInstance(x, y); };
+    types.pair = function(x, y) { return plt.baselib.lists.Cons.makeInstance(x, y); };
     types.hash = makeHashEqual;
     types.hashEq = makeHashEq;
 //     types.jsValue = function(name, val) { return new JsValue(name, val); };