diff --git a/js-assembler/package.rkt b/js-assembler/package.rkt
index 3936fc4..cad2582 100644
--- a/js-assembler/package.rkt
+++ b/js-assembler/package.rkt
@@ -159,7 +159,7 @@
              var modrec = M.modules[~s];
              var exports = {};
              modrec.isInvoked = true;
-             (function(MACHINE, RUNTIME, EXPORTS){~a})(M, plt.runtime, exports);
+             (function(MACHINE, EXPORTS){~a})(M, exports);
              ~a
              modrec.privateExports = exports;
              return M.control.pop().label(M);"
diff --git a/js-assembler/runtime-src/baselib-primitives.js b/js-assembler/runtime-src/baselib-primitives.js
index a9a918f..a2ced70 100644
--- a/js-assembler/runtime-src/baselib-primitives.js
+++ b/js-assembler/runtime-src/baselib-primitives.js
@@ -137,10 +137,10 @@
     installPrimitiveProcedure(
         'gensym',
         makeList(0, 1),
-        function(MACHINE) {
+        function(M) {
             var baseName = "g";
-            if (MACHINE.argcount === 1) {
-                baseName = checkSymbolOrString(MACHINE, 'gensym', 0).toString();
+            if (M.argcount === 1) {
+                baseName = checkSymbolOrString(M, 'gensym', 0).toString();
             }
             gensymCounter++;
             return new baselib.symbols.Symbol(baseName + gensymCounter);
@@ -150,13 +150,13 @@
     installPrimitiveProcedure(
         'display',
         makeList(1, 2),
-        function (MACHINE) {
-            var firstArg = MACHINE.env[MACHINE.env.length - 1];
-            var outputPort = MACHINE.params.currentOutputPort;
-            if (MACHINE.argcount === 2) {
-                outputPort = checkOutputPort(MACHINE, 'display', 1);
+        function (M) {
+            var firstArg = M.env[M.env.length - 1];
+            var outputPort = M.params.currentOutputPort;
+            if (M.argcount === 2) {
+                outputPort = checkOutputPort(M, 'display', 1);
             }
-            outputPort.writeDomNode(MACHINE, toDomNode(firstArg, 'display'));
+            outputPort.writeDomNode(M, toDomNode(firstArg, 'display'));
             return VOID;
         });
 
@@ -164,39 +164,39 @@
     installPrimitiveProcedure(
         'write-byte', 
         makeList(1, 2),
-        function (MACHINE) {
-            var firstArg = checkByte(MACHINE, 'write-byte', 0);
-            var outputPort = MACHINE.params.currentOutputPort;
-            if (MACHINE.argcount === 2) {
-                outputPort = checkOutputPort(MACHINE, 'display', 1);
+        function (M) {
+            var firstArg = checkByte(M, 'write-byte', 0);
+            var outputPort = M.params.currentOutputPort;
+            if (M.argcount === 2) {
+                outputPort = checkOutputPort(M, 'display', 1);
             }
-            outputPort.writeDomNode(MACHINE, toDomNode(String.fromCharCode(firstArg), 'display'));
+            outputPort.writeDomNode(M, toDomNode(String.fromCharCode(firstArg), 'display'));
             return VOID;
         });
 
 
     installPrimitiveProcedure(
         'newline', makeList(0, 1),
-        function (MACHINE) {
-            var outputPort = MACHINE.params.currentOutputPort;
-            if (MACHINE.argcount === 1) { 
-                outputPort = checkOutputPort(MACHINE, 'newline', 1);
+        function (M) {
+            var outputPort = M.params.currentOutputPort;
+            if (M.argcount === 1) { 
+                outputPort = checkOutputPort(M, 'newline', 1);
             }
-            outputPort.writeDomNode(MACHINE, toDomNode("\n", 'display'));
+            outputPort.writeDomNode(M, toDomNode("\n", 'display'));
             return VOID;
         });
 
     installPrimitiveProcedure(
         'displayln',
         makeList(1, 2),
-        function (MACHINE){
-            var firstArg = MACHINE.env[MACHINE.env.length-1];
-            var outputPort = MACHINE.params.currentOutputPort;
-            if (MACHINE.argcount === 2) {
-                outputPort = checkOutputPort(MACHINE, 'displayln', 1);
+        function (M){
+            var firstArg = M.env[M.env.length-1];
+            var outputPort = M.params.currentOutputPort;
+            if (M.argcount === 2) {
+                outputPort = checkOutputPort(M, 'displayln', 1);
             }
-            outputPort.writeDomNode(MACHINE, toDomNode(firstArg, 'display'));
-            outputPort.writeDomNode(MACHINE, toDomNode("\n", 'display'));
+            outputPort.writeDomNode(M, toDomNode(firstArg, 'display'));
+            outputPort.writeDomNode(M, toDomNode("\n", 'display'));
             return VOID;
         });
 
@@ -205,11 +205,11 @@
     installPrimitiveProcedure(
         'format',
         baselib.arity.makeArityAtLeast(1),
-        function (MACHINE) {
+        function (M) {
             var args = [], i, formatString;
-            formatString = checkString(MACHINE, 'format', 0).toString();
-            for(i = 1; i < MACHINE.argcount; i++) {
-                args.push(MACHINE.env[MACHINE.env.length - 1 - i]);
+            formatString = checkString(M, 'format', 0).toString();
+            for(i = 1; i < M.argcount; i++) {
+                args.push(M.env[M.env.length - 1 - i]);
             }
             return baselib.format.format(formatString, args, 'format');
         });
@@ -218,15 +218,15 @@
     installPrimitiveProcedure(
         'printf',
         baselib.arity.makeArityAtLeast(1),
-        function (MACHINE) {
+        function (M) {
             var args = [], i, formatString, result, outputPort;
-            formatString = checkString(MACHINE, 'printf', 0).toString();
-            for(i = 1; i < MACHINE.argcount; i++) {
-                args.push(MACHINE.env[MACHINE.env.length - 1 - i]);
+            formatString = checkString(M, 'printf', 0).toString();
+            for(i = 1; i < M.argcount; i++) {
+                args.push(M.env[M.env.length - 1 - i]);
             }
             result = baselib.format.format(formatString, args, 'format');
-            outputPort = MACHINE.params.currentOutputPort;            
-            outputPort.writeDomNode(MACHINE, toDomNode(result, 'display'));
+            outputPort = M.params.currentOutputPort;            
+            outputPort.writeDomNode(M, toDomNode(result, 'display'));
             return VOID;
         });
 
@@ -234,15 +234,15 @@
     installPrimitiveProcedure(
         'fprintf',
         baselib.arity.makeArityAtLeast(2),
-        function (MACHINE) {
+        function (M) {
             var args = [], i, formatString, outputPort, result;
-            outputPort = checkOutputPort(MACHINE, 'fprintf', 0);
-            formatString = checkString(MACHINE, 'fprintf', 1).toString();
-            for(i = 2; i < MACHINE.argcount; i++) {
-                args.push(MACHINE.env[MACHINE.env.length - 1 - i]);
+            outputPort = checkOutputPort(M, 'fprintf', 0);
+            formatString = checkString(M, 'fprintf', 1).toString();
+            for(i = 2; i < M.argcount; i++) {
+                args.push(M.env[M.env.length - 1 - i]);
             }
             result = baselib.format.format(formatString, args, 'format');
-            outputPort.writeDomNode(MACHINE, toDomNode(result, 'display'));
+            outputPort.writeDomNode(M, toDomNode(result, 'display'));
             return VOID;
         });
 
@@ -254,13 +254,13 @@
     installPrimitiveProcedure(
         'current-print',
         makeList(0, 1),
-        function (MACHINE) {
-            if (MACHINE.argcount === 1) {
-                MACHINE.params['currentPrint'] =                 
-                    checkProcedure(MACHINE, 'current-print', 0);
+        function (M) {
+            if (M.argcount === 1) {
+                M.params['currentPrint'] =                 
+                    checkProcedure(M, 'current-print', 0);
                 return VOID;
             } else {
-                return MACHINE.params['currentPrint'];
+                return M.params['currentPrint'];
             }
         });
 
@@ -268,13 +268,13 @@
     installPrimitiveProcedure(
         'current-output-port',
         makeList(0, 1),
-        function (MACHINE) {
-            if (MACHINE.argcount === 1) {
-                MACHINE.params['currentOutputPort'] = 
-                    checkOutputPort(MACHINE, 'current-output-port', 0);
+        function (M) {
+            if (M.argcount === 1) {
+                M.params['currentOutputPort'] = 
+                    checkOutputPort(M, 'current-output-port', 0);
                 return VOID;
             } else {
-                return MACHINE.params['currentOutputPort'];
+                return M.params['currentOutputPort'];
             }
         });
 
@@ -283,13 +283,13 @@
     installPrimitiveProcedure(
         'current-error-port',
         makeList(0, 1),
-        function (MACHINE) {
-            if (MACHINE.argcount === 1) {
-                MACHINE.params['currentErrorPort'] = 
-                    checkOutputPort(MACHINE, 'current-output-port', 0);
+        function (M) {
+            if (M.argcount === 1) {
+                M.params['currentErrorPort'] = 
+                    checkOutputPort(M, 'current-output-port', 0);
                 return VOID;
             } else {
-                return MACHINE.params['currentOutputPort'];
+                return M.params['currentOutputPort'];
             }
         });
 
@@ -302,11 +302,11 @@
     installPrimitiveProcedure(
         '=',
         baselib.arity.makeArityAtLeast(2),
-        function (MACHINE) {
+        function (M) {
 	    var i;
-            var firstArg = checkNumber(MACHINE, '=', 0), secondArg;
-            for (i = 1; i < MACHINE.argcount; i++) {
-                secondArg = checkNumber(MACHINE, '=', i);
+            var firstArg = checkNumber(M, '=', 0), secondArg;
+            for (i = 1; i < M.argcount; i++) {
+                secondArg = checkNumber(M, '=', i);
                 if (! (baselib.numbers.equals(firstArg, secondArg))) {
                     return false; 
                 }
@@ -319,10 +319,10 @@
     installPrimitiveProcedure(
         '=~',
         3,
-        function (MACHINE) {
-            var x = checkReal(MACHINE, '=~', 0);
-            var y = checkReal(MACHINE, '=~', 1);
-            var range = checkNonNegativeReal(MACHINE, '=~', 2);
+        function (M) {
+            var x = checkReal(M, '=~', 0);
+            var y = checkReal(M, '=~', 1);
+            var range = checkNonNegativeReal(M, '=~', 2);
             return baselib.numbers.lessThanOrEqual(
                 baselib.numbers.abs(baselib.numbers.subtract(x, y)), 
                 range);
@@ -331,10 +331,10 @@
 
 
     var makeChainingBinop = function (predicate, name) {
-        return function (MACHINE) {
-            var firstArg = checkNumber(MACHINE, name, 0), secondArg, i;
-            for (i = 1; i < MACHINE.argcount; i++) {
-                secondArg = checkNumber(MACHINE, name, i);
+        return function (M) {
+            var firstArg = checkNumber(M, name, 0), secondArg, i;
+            for (i = 1; i < M.argcount; i++) {
+                secondArg = checkNumber(M, name, i);
                 if (! (predicate(firstArg, secondArg))) {
                     return false; 
                 }
@@ -371,13 +371,13 @@
     installPrimitiveProcedure(
         '+',
         baselib.arity.makeArityAtLeast(0),
-        function (MACHINE) {
+        function (M) {
             var result = 0;
             var i = 0;
-            for (i = 0; i < MACHINE.argcount; i++) {
+            for (i = 0; i < M.argcount; i++) {
                 result = baselib.numbers.add(
                     result, 
-                    checkNumber(MACHINE, '+', i));
+                    checkNumber(M, '+', i));
             }
             return result;
         });
@@ -386,13 +386,13 @@
     installPrimitiveProcedure(
         '*',
         baselib.arity.makeArityAtLeast(0),
-        function (MACHINE) {
+        function (M) {
             var result = 1;
             var i = 0;
-            for (i=0; i < MACHINE.argcount; i++) {
+            for (i=0; i < M.argcount; i++) {
                 result = baselib.numbers.multiply(
                     result, 
-                    checkNumber(MACHINE, '*', i));
+                    checkNumber(M, '*', i));
             }
             return result;
         });
@@ -400,17 +400,17 @@
     installPrimitiveProcedure(
         '-',
         baselib.arity.makeArityAtLeast(1),
-        function (MACHINE) {
-            if (MACHINE.argcount === 1) { 
+        function (M) {
+            if (M.argcount === 1) { 
                 return baselib.numbers.subtract(
                     0, 
-                    checkNumber(MACHINE, '-', 0));
+                    checkNumber(M, '-', 0));
             }
-            var result = checkNumber(MACHINE, '-', 0), i;
-            for (i = 1; i < MACHINE.argcount; i++) {
+            var result = checkNumber(M, '-', 0), i;
+            for (i = 1; i < M.argcount; i++) {
                 result = baselib.numbers.subtract(
                     result, 
-                    checkNumber(MACHINE, '-', i));
+                    checkNumber(M, '-', i));
             }
             return result;
         });
@@ -418,12 +418,12 @@
     installPrimitiveProcedure(
         '/',
         baselib.arity.makeArityAtLeast(1),
-        function (MACHINE) {
-            var result = checkNumber(MACHINE, '/', 0), i;
-            for (i = 1; i < MACHINE.argcount; i++) {
+        function (M) {
+            var result = checkNumber(M, '/', 0), i;
+            for (i = 1; i < M.argcount; i++) {
                 result = baselib.numbers.divide(
                     result,
-                    checkNumber(MACHINE, '/', i));
+                    checkNumber(M, '/', i));
             }
             return result;
         });
@@ -432,8 +432,8 @@
     installPrimitiveProcedure(
         'add1',
         1,
-        function (MACHINE) {
-            var firstArg = checkNumber(MACHINE, 'add1', 0);
+        function (M) {
+            var firstArg = checkNumber(M, 'add1', 0);
             return baselib.numbers.add(firstArg, 1);
         });
 
@@ -441,8 +441,8 @@
     installPrimitiveProcedure(
         'sub1',
         1,
-        function (MACHINE) {
-            var firstArg = checkNumber(MACHINE, 'sub1', 0);
+        function (M) {
+            var firstArg = checkNumber(M, 'sub1', 0);
             return baselib.numbers.subtract(firstArg, 1);
         });
 
@@ -450,8 +450,8 @@
     installPrimitiveProcedure(
         'zero?',
         1,
-        function (MACHINE) {
-            var firstArg = MACHINE.env[MACHINE.env.length-1];
+        function (M) {
+            var firstArg = M.env[M.env.length-1];
             return baselib.numbers.equals(firstArg, 0);
         });
 
@@ -459,9 +459,9 @@
     installPrimitiveProcedure(
         'cons',
         2,
-        function (MACHINE) {
-            var firstArg = MACHINE.env[MACHINE.env.length-1];
-            var secondArg = MACHINE.env[MACHINE.env.length-2];
+        function (M) {
+            var firstArg = M.env[M.env.length-1];
+            var secondArg = M.env[M.env.length-2];
             return makePair(firstArg, secondArg);
         });
 
@@ -469,10 +469,10 @@
     installPrimitiveProcedure(
         'list',
         baselib.arity.makeArityAtLeast(0),
-        function (MACHINE) {
+        function (M) {
             var result = NULL, i;
-            for (i = 0; i < MACHINE.argcount; i++) {
-                result = makePair(MACHINE.env[MACHINE.env.length - (MACHINE.argcount - i)],
+            for (i = 0; i < M.argcount; i++) {
+                result = makePair(M.env[M.env.length - (M.argcount - i)],
                                   result);
             }
             return result;
@@ -481,10 +481,10 @@
     installPrimitiveProcedure(
         'list*',
         baselib.arity.makeArityAtLeast(1),
-        function (MACHINE) {
-            var result = checkList(MACHINE, 'list*', MACHINE.argcount - 1), i;
-            for (i = MACHINE.argcount - 2; i >= 0; i--) {
-                result = makePair(MACHINE.env[MACHINE.env.length - 1 - i],
+        function (M) {
+            var result = checkList(M, 'list*', M.argcount - 1), i;
+            for (i = M.argcount - 2; i >= 0; i--) {
+                result = makePair(M.env[M.env.length - 1 - i],
                                   result);
             }
             return result;
@@ -494,9 +494,9 @@
     installPrimitiveProcedure(
         'list-ref',
         2,
-        function (MACHINE) {
-            var lst = checkList(MACHINE, 'list-ref', 0);
-            var index = checkNaturalInRange(MACHINE, 'list-ref', 1,
+        function (M) {
+            var lst = checkList(M, 'list-ref', 0);
+            var index = checkNaturalInRange(M, 'list-ref', 1,
                                             0, baselib.lists.length(lst));
             return baselib.lists.listRef(lst, baselib.numbers.toFixnum(index));
         });
@@ -507,24 +507,24 @@
     installPrimitiveProcedure(
         'car',
         1,
-        function (MACHINE) {
-            var firstArg = checkPair(MACHINE, 'car', 0);
+        function (M) {
+            var firstArg = checkPair(M, 'car', 0);
             return firstArg.first;
         });
 
     installPrimitiveProcedure(
         'cdr',
         1,
-        function (MACHINE) {
-            var firstArg = checkPair(MACHINE, 'cdr', 0);
+        function (M) {
+            var firstArg = checkPair(M, 'cdr', 0);
             return firstArg.rest;
         });
 
     installPrimitiveProcedure(
         'pair?',
         1,
-        function (MACHINE) {
-            var firstArg = MACHINE.env[MACHINE.env.length-1];
+        function (M) {
+            var firstArg = M.env[M.env.length-1];
             return isPair(firstArg);
         });
 
@@ -532,17 +532,17 @@
     installPrimitiveProcedure(
         'list?',
         1,
-        function (MACHINE) {
-            return isList(MACHINE.env[MACHINE.env.length -1]);
+        function (M) {
+            return isList(M.env[M.env.length -1]);
         });
 
 
     installPrimitiveProcedure(
         'set-car!',
         2,
-        function (MACHINE) {
-            var firstArg = checkPair(MACHINE, 'set-car!', 0);
-            var secondArg = MACHINE.env[MACHINE.env.length-2];
+        function (M) {
+            var firstArg = checkPair(M, 'set-car!', 0);
+            var secondArg = M.env[M.env.length-2];
             firstArg.first = secondArg;
             return VOID;
         });
@@ -551,9 +551,9 @@
     installPrimitiveProcedure(
         'set-cdr!',
         2,
-        function (MACHINE) {
-            var firstArg = checkPair(MACHINE, 'set-car!', 0);
-            var secondArg = MACHINE.env[MACHINE.env.length-2];
+        function (M) {
+            var firstArg = checkPair(M, 'set-car!', 0);
+            var secondArg = M.env[M.env.length-2];
             firstArg.rest = secondArg;
             return VOID;
         });
@@ -562,8 +562,8 @@
     installPrimitiveProcedure(
         'not',
         1,
-        function (MACHINE) {
-            var firstArg = MACHINE.env[MACHINE.env.length-1];
+        function (M) {
+            var firstArg = M.env[M.env.length-1];
             return (firstArg === false);
         });
 
@@ -571,8 +571,8 @@
     installPrimitiveProcedure(
         'null?',
         1,
-        function (MACHINE) {
-            var firstArg = MACHINE.env[MACHINE.env.length-1];
+        function (M) {
+            var firstArg = M.env[M.env.length-1];
             return firstArg === NULL;
         });
 
@@ -580,11 +580,11 @@
     installPrimitiveProcedure(
         'vector',
         baselib.arity.makeArityAtLeast(0),
-        function (MACHINE) {
+        function (M) {
             var i;
             var result = [];
-            for (i = 0; i < MACHINE.argcount; i++) {
-                result.push(MACHINE.env[MACHINE.env.length-1-i]);
+            for (i = 0; i < M.argcount; i++) {
+                result.push(M.env[M.env.length-1-i]);
             }
             var newVector = makeVector.apply(null, result);
             return newVector;
@@ -594,12 +594,12 @@
     installPrimitiveProcedure(
         'make-vector',
         makeList(1, 2),
-        function (MACHINE) {
+        function (M) {
             var value = 0;
             var length = baselib.numbers.toFixnum(
-                checkNatural(MACHINE, 'make-vector', 0));
-            if (MACHINE.argcount === 2) {
-                value = MACHINE.env[MACHINE.env.length - 2];
+                checkNatural(M, 'make-vector', 0));
+            if (M.argcount === 2) {
+                value = M.env[M.env.length - 2];
             }
             var arr = [];
 	    var i;
@@ -613,8 +613,8 @@
     installPrimitiveProcedure(
         'vector->list',
         1,
-        function (MACHINE) {
-            var elts = checkVector(MACHINE, 'vector->list', 0).elts;
+        function (M) {
+            var elts = checkVector(M, 'vector->list', 0).elts;
             var i;
             var result = NULL;
             for (i = 0; i < elts.length; i++) {
@@ -627,8 +627,8 @@
     installPrimitiveProcedure(
         'list->vector',
         1,
-        function (MACHINE) {
-            var firstArg = checkList(MACHINE, 'list->vector', 0);
+        function (M) {
+            var firstArg = checkList(M, 'list->vector', 0);
             var result = [];
             while (firstArg !== NULL) {
                 result.push(firstArg.first);
@@ -641,9 +641,9 @@
     installPrimitiveProcedure(
         'vector-ref',
         2,
-        function (MACHINE) {
-            var elts = checkVector(MACHINE, 'vector-ref', 0).elts;
-            var index = MACHINE.env[MACHINE.env.length-2];
+        function (M) {
+            var elts = checkVector(M, 'vector-ref', 0).elts;
+            var index = M.env[M.env.length-2];
             return elts[index];
         });
 
@@ -651,13 +651,13 @@
     installPrimitiveProcedure(
         'vector-set!',
         3,
-        function (MACHINE) {
-            var elts = checkVector(MACHINE, 'vector-set!', 0).elts;
+        function (M) {
+            var elts = checkVector(M, 'vector-set!', 0).elts;
             // FIXME: check out-of-bounds vector
             var index = baselib.numbers.toFixnum(
-                checkNaturalInRange(MACHINE, 'vector-set!', 1,
+                checkNaturalInRange(M, 'vector-set!', 1,
                                     0, elts.length));
-            var val = MACHINE.env[MACHINE.env.length - 1 - 2];
+            var val = M.env[M.env.length - 1 - 2];
             elts[index] = val;
             return VOID;
         });
@@ -666,8 +666,8 @@
     installPrimitiveProcedure(
         'vector-length',
         1,
-        function (MACHINE) {
-            return checkVector(MACHINE, 'vector-length', 0).elts.length;
+        function (M) {
+            return checkVector(M, 'vector-length', 0).elts.length;
         });
 
 
@@ -675,12 +675,12 @@
     installPrimitiveProcedure(
         'make-string',
         makeList(1, 2),
-        function (MACHINE) {
+        function (M) {
             var value = String.fromCharCode(0);
             var length = baselib.numbers.toFixnum(
-                checkNatural(MACHINE, 'make-string', 0));
-            if (MACHINE.argcount === 2) {
-                value = checkChar(MACHINE, 'make-string', 1).val;
+                checkNatural(M, 'make-string', 0));
+            if (M.argcount === 2) {
+                value = checkChar(M, 'make-string', 1).val;
             }
             var arr = [];
 	    var i;
@@ -693,12 +693,12 @@
     installPrimitiveProcedure(
         'substring',
         makeList(2, 3),
-        function(MACHINE) {
-            var str = String(checkString(MACHINE, 'substring', 0));
-            var start = baselib.numbers.toFixnum(checkNatural(MACHINE, 'substring', 1));
+        function(M) {
+            var str = String(checkString(M, 'substring', 0));
+            var start = baselib.numbers.toFixnum(checkNatural(M, 'substring', 1));
             var end = str.length;
-            if (MACHINE.argcount === 3) {
-                end = baselib.numbers.toFixnum(checkNatural(MACHINE, 'substring', 2));
+            if (M.argcount === 3) {
+                end = baselib.numbers.toFixnum(checkNatural(M, 'substring', 2));
             }
             return str.substring(start, end);
         });
@@ -707,8 +707,8 @@
     installPrimitiveProcedure(
         'list->string',
         1,
-        function (MACHINE) {
-            var firstArg = checkListofChars(MACHINE, 'list->string', 0);
+        function (M) {
+            var firstArg = checkListofChars(M, 'list->string', 0);
             var result = [];
             while (firstArg !== NULL) {
                 result.push(firstArg.first.val);
@@ -721,11 +721,11 @@
     installPrimitiveProcedure(
         'string',
         baselib.arity.makeArityAtLeast(0),
-        function (MACHINE) {
+        function (M) {
             var i;
             var chars = [];
-            for (i = 0; i < MACHINE.argcount; i++) {
-                chars.push(checkChar(MACHINE, 'string', i).val);
+            for (i = 0; i < M.argcount; i++) {
+                chars.push(checkChar(M, 'string', i).val);
             }
             return chars.join('');
         });
@@ -734,8 +734,8 @@
     installPrimitiveProcedure(
         'string->list',
         1,
-        function (MACHINE) {
-            var str = checkString(MACHINE, 'string->list', 0).toString();
+        function (M) {
+            var str = checkString(M, 'string->list', 0).toString();
             var i;
             var result = NULL;
             for (i = str.length - 1; i >= 0; i--) {
@@ -749,10 +749,10 @@
     installPrimitiveProcedure(
         'string-set!',
         3,
-        function (MACHINE) {
-            var str = checkMutableString(MACHINE, 'string-set!', 0);
-            var k = checkNatural(MACHINE, 'string-set!', 1);
-            var ch = checkChar(MACHINE, 'string-set!', 2);
+        function (M) {
+            var str = checkMutableString(M, 'string-set!', 0);
+            var k = checkNatural(M, 'string-set!', 1);
+            var ch = checkChar(M, 'string-set!', 2);
 	    str.set(baselib.numbers.toFixnum(k), ch.val);
             return VOID;
         });
@@ -764,16 +764,16 @@
     installPrimitiveProcedure(
         'symbol?',
         1,
-        function (MACHINE) {
-            var firstArg = MACHINE.env[MACHINE.env.length-1];
+        function (M) {
+            var firstArg = M.env[M.env.length-1];
             return isSymbol(firstArg);
         });
 
     installPrimitiveProcedure(
         'symbol->string',
         1,
-        function (MACHINE) {
-            var firstArg = checkSymbol(MACHINE, 'symbol->string', 0);
+        function (M) {
+            var firstArg = checkSymbol(M, 'symbol->string', 0);
             return firstArg.toString();
         });
 
@@ -781,11 +781,11 @@
     installPrimitiveProcedure(
         'string=?',
         baselib.arity.makeArityAtLeast(1),
-        function (MACHINE) {
-            var s = checkString(MACHINE, 'string=?', 0).toString();
+        function (M) {
+            var s = checkString(M, 'string=?', 0).toString();
 	    var i;
-            for (i = 1; i < MACHINE.argcount; i++) {
-                if (s !== checkString(MACHINE, 'string=?', i).toString()) {
+            for (i = 1; i < M.argcount; i++) {
+                if (s !== checkString(M, 'string=?', i).toString()) {
                     return false;
                 }
             }
@@ -796,11 +796,11 @@
     installPrimitiveProcedure(
         'string<=?',
         baselib.arity.makeArityAtLeast(1),
-        function (MACHINE) {
-            var s = checkString(MACHINE, 'string<=?', 0).toString();
+        function (M) {
+            var s = checkString(M, 'string<=?', 0).toString();
 	    var i;
-            for (i = 1; i < MACHINE.argcount; i++) {
-                if ((s <= checkString(MACHINE, 'string<=?', i).toString()) === false) {
+            for (i = 1; i < M.argcount; i++) {
+                if ((s <= checkString(M, 'string<=?', i).toString()) === false) {
                     return false;
                 }
             }
@@ -810,11 +810,11 @@
     installPrimitiveProcedure(
         'string<?',
         baselib.arity.makeArityAtLeast(1),
-        function (MACHINE) {
-            var s = checkString(MACHINE, 'string<?', 0).toString();
+        function (M) {
+            var s = checkString(M, 'string<?', 0).toString();
 	    var i;
-            for (i = 1; i < MACHINE.argcount; i++) {
-                if ((s < checkString(MACHINE, 'string<?', i).toString()) === false) {
+            for (i = 1; i < M.argcount; i++) {
+                if ((s < checkString(M, 'string<?', i).toString()) === false) {
                     return false;
                 }
             }
@@ -824,11 +824,11 @@
     installPrimitiveProcedure(
         'string>=?',
         baselib.arity.makeArityAtLeast(1),
-        function (MACHINE) {
-            var s = checkString(MACHINE, 'string>=?', 0).toString();
+        function (M) {
+            var s = checkString(M, 'string>=?', 0).toString();
 	    var i;
-            for (i = 1; i < MACHINE.argcount; i++) {
-                if ((s >= checkString(MACHINE, 'string>=?', i).toString()) === false) {
+            for (i = 1; i < M.argcount; i++) {
+                if ((s >= checkString(M, 'string>=?', i).toString()) === false) {
                     return false;
                 }
             }
@@ -838,11 +838,11 @@
     installPrimitiveProcedure(
         'string>?',
         baselib.arity.makeArityAtLeast(1),
-        function (MACHINE) {
-            var s = checkString(MACHINE, 'string>?', 0).toString();
+        function (M) {
+            var s = checkString(M, 'string>?', 0).toString();
 	    var i;
-            for (i = 1; i < MACHINE.argcount; i++) {
-                if ((s > checkString(MACHINE, 'string>?', i).toString()) === false) {
+            for (i = 1; i < M.argcount; i++) {
+                if ((s > checkString(M, 'string>?', i).toString()) === false) {
                     return false;
                 }
             }
@@ -869,11 +869,11 @@
     installPrimitiveProcedure(
         'string-ci=?',
         baselib.arity.makeArityAtLeast(1),
-        function (MACHINE) {
-            var s = checkString(MACHINE, 'string-ci=?', 0).toString().toUpperCase();
+        function (M) {
+            var s = checkString(M, 'string-ci=?', 0).toString().toUpperCase();
 	    var i;
-            for (i = 1; i < MACHINE.argcount; i++) {
-                if (s !== checkString(MACHINE, 'string-ci=?', i).toString().toUpperCase()) {
+            for (i = 1; i < M.argcount; i++) {
+                if (s !== checkString(M, 'string-ci=?', i).toString().toUpperCase()) {
                     return false;
                 }
             }
@@ -884,11 +884,11 @@
     installPrimitiveProcedure(
         'string-ci<=?',
         baselib.arity.makeArityAtLeast(1),
-        function (MACHINE) {
-            var s = checkString(MACHINE, 'string-ci<=?', 0).toString().toUpperCase();
+        function (M) {
+            var s = checkString(M, 'string-ci<=?', 0).toString().toUpperCase();
 	    var i;
-            for (i = 1; i < MACHINE.argcount; i++) {
-                if ((s <= checkString(MACHINE, 'string-ci<=?', i).toString().toUpperCase()) === false) {
+            for (i = 1; i < M.argcount; i++) {
+                if ((s <= checkString(M, 'string-ci<=?', i).toString().toUpperCase()) === false) {
                     return false;
                 }
             }
@@ -898,11 +898,11 @@
     installPrimitiveProcedure(
         'string-ci<?',
         baselib.arity.makeArityAtLeast(1),
-        function (MACHINE) {
-            var s = checkString(MACHINE, 'string-ci<?', 0).toString().toUpperCase();
+        function (M) {
+            var s = checkString(M, 'string-ci<?', 0).toString().toUpperCase();
 	    var i;
-            for (i = 1; i < MACHINE.argcount; i++) {
-                if ((s < checkString(MACHINE, 'string-ci<?', i).toString().toUpperCase()) === false) {
+            for (i = 1; i < M.argcount; i++) {
+                if ((s < checkString(M, 'string-ci<?', i).toString().toUpperCase()) === false) {
                     return false;
                 }
             }
@@ -912,11 +912,11 @@
     installPrimitiveProcedure(
         'string-ci>=?',
         baselib.arity.makeArityAtLeast(1),
-        function (MACHINE) {
-            var s = checkString(MACHINE, 'string-ci>=?', 0).toString().toUpperCase();
+        function (M) {
+            var s = checkString(M, 'string-ci>=?', 0).toString().toUpperCase();
 	    var i;
-            for (i = 1; i < MACHINE.argcount; i++) {
-                if ((s >= checkString(MACHINE, 'string-ci>=?', i).toString().toUpperCase()) === false) {
+            for (i = 1; i < M.argcount; i++) {
+                if ((s >= checkString(M, 'string-ci>=?', i).toString().toUpperCase()) === false) {
                     return false;
                 }
             }
@@ -926,11 +926,11 @@
     installPrimitiveProcedure(
         'string-ci>?',
         baselib.arity.makeArityAtLeast(1),
-        function (MACHINE) {
-            var s = checkString(MACHINE, 'string-ci>?', 0).toString().toUpperCase();
+        function (M) {
+            var s = checkString(M, 'string-ci>?', 0).toString().toUpperCase();
 	    var i;
-            for (i = 1; i < MACHINE.argcount; i++) {
-                if ((s > checkString(MACHINE, 'string-ci>?', i).toString().toUpperCase()) === false) {
+            for (i = 1; i < M.argcount; i++) {
+                if ((s > checkString(M, 'string-ci>?', i).toString().toUpperCase()) === false) {
                     return false;
                 }
             }
@@ -944,11 +944,11 @@
     installPrimitiveProcedure(
         'string-append',
         baselib.arity.makeArityAtLeast(0),
-        function (MACHINE) {
+        function (M) {
             var buffer = [];
             var i;
-            for (i = 0; i < MACHINE.argcount; i++) {
-                buffer.push(checkString(MACHINE, 'string-append', i).toString());
+            for (i = 0; i < M.argcount; i++) {
+                buffer.push(checkString(M, 'string-append', i).toString());
             }
             return buffer.join('');
         });
@@ -956,8 +956,8 @@
     installPrimitiveProcedure(
         'string-length',
         1,
-        function (MACHINE) {
-            var firstArg = checkString(MACHINE, 'string-length', 0).toString();
+        function (M) {
+            var firstArg = checkString(M, 'string-length', 0).toString();
             return firstArg.length;
         });
 
@@ -965,10 +965,10 @@
     installPrimitiveProcedure(
         'string-ref',
         2,
-        function (MACHINE) {
-            var firstArg = checkString(MACHINE, 'string-ref', 0).toString();
+        function (M) {
+            var firstArg = checkString(M, 'string-ref', 0).toString();
             var index = baselib.numbers.toFixnum(
-                checkNaturalInRange(MACHINE, 'string-ref', 1,
+                checkNaturalInRange(M, 'string-ref', 1,
                                     0, firstArg.length));
             return baselib.chars.makeChar(firstArg[index]);
         });
@@ -978,41 +978,41 @@
     installPrimitiveProcedure(
         'string?',
         1,
-        function (MACHINE) {
-            return isString(MACHINE.env[MACHINE.env.length - 1]);
+        function (M) {
+            return isString(M.env[M.env.length - 1]);
         });
 
 
     installPrimitiveProcedure(
         'number->string',
         1,
-        function (MACHINE) {
-            return checkNumber(MACHINE, 'number->string', 0).toString();
+        function (M) {
+            return checkNumber(M, 'number->string', 0).toString();
         });
 
 
     installPrimitiveProcedure(
         'string->symbol',
         1,
-        function (MACHINE) {
-            return makeSymbol(checkString(MACHINE, 'string->symbol', 0).toString());
+        function (M) {
+            return makeSymbol(checkString(M, 'string->symbol', 0).toString());
         });
 
 
     installPrimitiveProcedure(
         'string->number',
         1,
-        function (MACHINE) {
+        function (M) {
             return baselib.numbers.fromString(
-                checkString(MACHINE, 'string->number', 0).toString());
+                checkString(M, 'string->number', 0).toString());
         });
 
 
     installPrimitiveProcedure(
         'boolean?',
         1,
-        function(MACHINE) {
-            var v = MACHINE.env[MACHINE.env.length - 1];
+        function(M) {
+            var v = M.env[M.env.length - 1];
             return (v === true || v === false);
         });
 
@@ -1020,19 +1020,19 @@
     installPrimitiveProcedure(
         'char?',
         1,
-        function(MACHINE) {
-            return baselib.chars.isChar(MACHINE.env[MACHINE.env.length -1 ]);
+        function(M) {
+            return baselib.chars.isChar(M.env[M.env.length -1 ]);
         });
 
 
     installPrimitiveProcedure(
         'char=?',
         baselib.arity.makeArityAtLeast(2),
-        function(MACHINE) {
-            var s = checkChar(MACHINE, 'char=?', 0).val;
+        function(M) {
+            var s = checkChar(M, 'char=?', 0).val;
 	    var i;
-            for (i = 1; i < MACHINE.argcount; i++) {
-                if (checkChar(MACHINE, 'char=?', i).val !== s) {
+            for (i = 1; i < M.argcount; i++) {
+                if (checkChar(M, 'char=?', i).val !== s) {
                     return false;
                 }
             }
@@ -1043,16 +1043,16 @@
     installPrimitiveProcedure(
         'char-upcase',
         1,
-        function(MACHINE) {
-            var ch = checkChar(MACHINE, 'char=?', 0).val;
+        function(M) {
+            var ch = checkChar(M, 'char=?', 0).val;
             return baselib.chars.makeChar(ch.toUpperCase());
         });
 
     installPrimitiveProcedure(
         'char-downcase',
         1,
-        function(MACHINE) {
-            var ch = checkChar(MACHINE, 'char=?', 0).val;
+        function(M) {
+            var ch = checkChar(M, 'char=?', 0).val;
             return baselib.chars.makeChar(ch.toLowerCase());
         });
 
@@ -1063,25 +1063,25 @@
     installPrimitiveProcedure(
         'box',
         1,
-        function (MACHINE) {
-            var firstArg = MACHINE.env[MACHINE.env.length-1];
+        function (M) {
+            var firstArg = M.env[M.env.length-1];
             return makeBox(firstArg);
         });
 
     installPrimitiveProcedure(
         'unbox',
         1,
-        function (MACHINE) {
-            var firstArg = checkBox(MACHINE, 'unbox', 0);
+        function (M) {
+            var firstArg = checkBox(M, 'unbox', 0);
             return firstArg.ref();
         });
 
     installPrimitiveProcedure(
         'set-box!',
         2,
-        function (MACHINE) {
-            var firstArg = checkMutableBox(MACHINE, 'set-box!', 0);
-            var secondArg = MACHINE.env[MACHINE.env.length-2];
+        function (M) {
+            var firstArg = checkMutableBox(M, 'set-box!', 0);
+            var secondArg = M.env[M.env.length-2];
             firstArg.set(secondArg);
             return VOID;
         });
@@ -1089,7 +1089,7 @@
     installPrimitiveProcedure(
         'void',
         baselib.arity.makeArityAtLeast(0),
-        function (MACHINE) {
+        function (M) {
             return VOID;
         });
 
@@ -1097,11 +1097,11 @@
     installPrimitiveProcedure(
         'random',
         baselib.lists.makeList(0, 1),
-        function (MACHINE) {
-            if (MACHINE.argcount === 0) {
+        function (M) {
+            if (M.argcount === 0) {
                 return makeFloat(Math.random());
             } else {
-                var n = checkNatural(MACHINE, 'random', 0);
+                var n = checkNatural(M, 'random', 0);
                 return Math.floor(Math.random() * baselib.numbers.toFixnum(n));
             }
         });
@@ -1110,18 +1110,18 @@
     installPrimitiveProcedure(
         'eq?',
         2,
-        function (MACHINE) {
-            var firstArg = MACHINE.env[MACHINE.env.length-1];
-            var secondArg = MACHINE.env[MACHINE.env.length-2];
+        function (M) {
+            var firstArg = M.env[M.env.length-1];
+            var secondArg = M.env[M.env.length-2];
             return firstArg === secondArg;
         });
 
     installPrimitiveProcedure(
         'eqv?',
         2,
-        function (MACHINE) {
-            var firstArg = MACHINE.env[MACHINE.env.length-1];
-            var secondArg = MACHINE.env[MACHINE.env.length-2];
+        function (M) {
+            var firstArg = M.env[M.env.length-1];
+            var secondArg = M.env[M.env.length-2];
             return baselib.equality.eqv(firstArg, secondArg);
         });
 
@@ -1130,9 +1130,9 @@
     installPrimitiveProcedure(
         'equal?',
         2,
-        function (MACHINE) {
-            var firstArg = MACHINE.env[MACHINE.env.length-1];
-            var secondArg = MACHINE.env[MACHINE.env.length-2];
+        function (M) {
+            var firstArg = M.env[M.env.length-1];
+            var secondArg = M.env[M.env.length-2];
             return equals(firstArg, secondArg);
         });
 
@@ -1140,24 +1140,24 @@
     // This definition of apply will take precedence over the
     // implementation of apply in the boostrapped-primitives.rkt,
     // since it provides nicer error handling.
-    var applyImplementation = function (MACHINE) {
-        if(--MACHINE.callsBeforeTrampoline < 0) { 
+    var applyImplementation = function (M) {
+        if(--M.callsBeforeTrampoline < 0) { 
             throw applyImplementation;
         }
-        var proc = checkProcedure(MACHINE, 'apply', 0);
-        MACHINE.env.pop();
-        MACHINE.argcount--;
-        checkList(MACHINE, 'apply', MACHINE.argcount - 1);
-        MACHINE.spliceListIntoStack(MACHINE.argcount - 1);
-        if (baselib.arity.isArityMatching(proc.racketArity, MACHINE.argcount)) {
-            MACHINE.proc = proc;
+        var proc = checkProcedure(M, 'apply', 0);
+        M.env.pop();
+        M.argcount--;
+        checkList(M, 'apply', M.argcount - 1);
+        M.spliceListIntoStack(M.argcount - 1);
+        if (baselib.arity.isArityMatching(proc.racketArity, M.argcount)) {
+            M.proc = proc;
             if (baselib.functions.isPrimitiveProcedure(proc)) {
-                return finalizeClosureCall(MACHINE, proc(MACHINE));
+                return finalizeClosureCall(M, proc(M));
             } else {
-                return proc.label(MACHINE);
+                return proc.label(M);
             }
         } else {
-            raiseArityMismatchError(MACHINE, proc, MACHINE.argcount);
+            raiseArityMismatchError(M, proc, M.argcount);
         }
     };
     installPrimitiveClosure(
@@ -1177,24 +1177,24 @@
     installPrimitiveProcedure(
         'procedure?',
         1,
-        function (MACHINE) {
-            return baselib.functions.isProcedure(MACHINE.env[MACHINE.env.length - 1]);
+        function (M) {
+            return baselib.functions.isProcedure(M.env[M.env.length - 1]);
         });
     
     installPrimitiveProcedure(
         'procedure-arity-includes?',
         2,
-        function (MACHINE) {
-            var proc = checkProcedure(MACHINE, 'procedure-arity-includes?', 0);
-            var argcount = checkNatural(MACHINE, 'procedure-arity-includes?', 1);
+        function (M) {
+            var proc = checkProcedure(M, 'procedure-arity-includes?', 0);
+            var argcount = checkNatural(M, 'procedure-arity-includes?', 1);
             return baselib.arity.isArityMatching(proc.racketArity, argcount);
         });
 
     installPrimitiveProcedure(
         'procedure-arity',
         1,
-        function (MACHINE) {
-            var proc = checkProcedure(MACHINE, 'procedure-arity-includes?', 0);
+        function (M) {
+            var proc = checkProcedure(M, 'procedure-arity-includes?', 0);
             return proc.racketArity;
         });
 
@@ -1202,9 +1202,9 @@
     installPrimitiveProcedure(
         'procedure-rename',
         2,
-        function (MACHINE) {
-            var proc = checkProcedure(MACHINE, 'procedure-rename', 0);
-            var name = checkSymbol(MACHINE, 'procedure-rename', 1);
+        function (M) {
+            var proc = checkProcedure(M, 'procedure-rename', 0);
+            var name = checkSymbol(M, 'procedure-rename', 1);
             return baselib.functions.renameProcedure(proc, name);
         });
 
@@ -1213,19 +1213,19 @@
     installPrimitiveProcedure(
         'member',
         2,
-        function (MACHINE) {
-            var x = MACHINE.env[MACHINE.env.length-1];
-            var lst = MACHINE.env[MACHINE.env.length-2];
+        function (M) {
+            var x = M.env[M.env.length-1];
+            var lst = M.env[M.env.length-2];
             while (true) {
                 if (lst === NULL) {
                     return false;
                 }
                 if (! isPair(lst)) {
-                    raiseArgumentTypeError(MACHINE,
+                    raiseArgumentTypeError(M,
                                            'member',
                                            'list',
                                            1,
-                                           MACHINE.env[MACHINE.env.length - 1 - 1]);
+                                           M.env[M.env.length - 1 - 1]);
                 }
                 if (equals(x, (lst.first))) {
                     return lst;
@@ -1239,11 +1239,11 @@
     installPrimitiveProcedure(
         'reverse',
         1,
-        function (MACHINE) {
+        function (M) {
             var rev = NULL;
-            var lst = MACHINE.env[MACHINE.env.length-1];
+            var lst = M.env[M.env.length-1];
             while(lst !== NULL) {
-                rev = makePair(testArgument(MACHINE, 'pair', isPair, lst, 0, 'reverse').first,
+                rev = makePair(testArgument(M, 'pair', isPair, lst, 0, 'reverse').first,
                                rev);
                 lst = lst.rest;
             }
@@ -1256,43 +1256,43 @@
     installPrimitiveProcedure(
 	'number?',
 	1,
-	function(MACHINE) {
-	    return isNumber(MACHINE.env[MACHINE.env.length - 1]);
+	function(M) {
+	    return isNumber(M.env[M.env.length - 1]);
 	});
 
     installPrimitiveProcedure(
 	'real?',
 	1,
-	function(MACHINE) {
-	    return isReal(MACHINE.env[MACHINE.env.length - 1]);
+	function(M) {
+	    return isReal(M.env[M.env.length - 1]);
 	});
     installPrimitiveProcedure(
 	'complex?',
 	1,
-	function(MACHINE) {
-	    return isComplex(MACHINE.env[MACHINE.env.length - 1]);
+	function(M) {
+	    return isComplex(M.env[M.env.length - 1]);
 	});
 
     installPrimitiveProcedure(
 	'rational?',
 	1,
-	function(MACHINE) {
-	    return isRational(MACHINE.env[MACHINE.env.length - 1]);
+	function(M) {
+	    return isRational(M.env[M.env.length - 1]);
 	});
 
     installPrimitiveProcedure(
         'even?',
         1,
-        function(MACHINE) {
-            var n = checkInteger(MACHINE, 'even?', 0);
+        function(M) {
+            var n = checkInteger(M, 'even?', 0);
             return baselib.numbers.equals(0, baselib.numbers.modulo(n, 2));
         });
 
     installPrimitiveProcedure(
         'odd?',
         1,
-        function(MACHINE) {
-            var n = checkInteger(MACHINE, 'odd?', 0);
+        function(M) {
+            var n = checkInteger(M, 'odd?', 0);
             return baselib.numbers.equals(1, baselib.numbers.modulo(n, 2));
         });
 
@@ -1300,16 +1300,16 @@
     installPrimitiveProcedure(
         'positive?',
         1,
-        function(MACHINE) {
-            var n = checkReal(MACHINE, 'positive?', 0);
+        function(M) {
+            var n = checkReal(M, 'positive?', 0);
             return baselib.numbers.greaterThan(n, 0);
         });
 
     installPrimitiveProcedure(
         'negative?',
         1,
-        function(MACHINE) {
-            var n = checkReal(MACHINE, 'negative?', 0);
+        function(M) {
+            var n = checkReal(M, 'negative?', 0);
             return baselib.numbers.lessThan(n, 0);
         });
 
@@ -1321,34 +1321,34 @@
     installPrimitiveProcedure(
         'abs',
         1,
-        function (MACHINE) {
+        function (M) {
             return baselib.numbers.abs(
-                checkNumber(MACHINE, 'abs', 0));
+                checkNumber(M, 'abs', 0));
         });
 
     installPrimitiveProcedure(
         'acos',
         1,
-        function (MACHINE) {
+        function (M) {
             return baselib.numbers.acos(
-                checkNumber(MACHINE, 'acos', 0));
+                checkNumber(M, 'acos', 0));
         });
 
 
     installPrimitiveProcedure(
         'asin',
         1,
-        function (MACHINE) {
+        function (M) {
             return baselib.numbers.asin(
-                checkNumber(MACHINE, 'asin', 0));
+                checkNumber(M, 'asin', 0));
         });
 
     installPrimitiveProcedure(
         'sin',
         1,
-        function (MACHINE) {
+        function (M) {
             return baselib.numbers.sin(
-                checkNumber(MACHINE, 'sin', 0));
+                checkNumber(M, 'sin', 0));
         });
 
 
@@ -1356,18 +1356,18 @@
     installPrimitiveProcedure(
         'sinh',
         1,
-        function (MACHINE) {
+        function (M) {
             return baselib.numbers.sinh(
-                checkNumber(MACHINE, 'sinh', 0));
+                checkNumber(M, 'sinh', 0));
         });
 
 
     installPrimitiveProcedure(
         'tan',
         1,
-        function (MACHINE) {
+        function (M) {
             return baselib.numbers.tan(
-                checkNumber(MACHINE, 'tan', 0));
+                checkNumber(M, 'tan', 0));
         });
 
     
@@ -1375,15 +1375,15 @@
     installPrimitiveProcedure(
         'atan',
         makeList(1, 2),
-        function (MACHINE) {
-            if (MACHINE.argcount === 1) {
+        function (M) {
+            if (M.argcount === 1) {
                 return baselib.numbers.atan(
-                    checkNumber(MACHINE, 'atan', 0));
+                    checkNumber(M, 'atan', 0));
             } else {
                 return makeFloat(
                     Math.atan2(
-                        baselib.numbers.toFixnum(checkNumber(MACHINE, 'atan', 0)),
-                        baselib.numbers.toFixnum(checkNumber(MACHINE, 'atan', 1))));
+                        baselib.numbers.toFixnum(checkNumber(M, 'atan', 0)),
+                        baselib.numbers.toFixnum(checkNumber(M, 'atan', 1))));
             }
         });
 
@@ -1391,25 +1391,25 @@
     installPrimitiveProcedure(
         'angle',
         1,
-        function (MACHINE) {
+        function (M) {
             return baselib.numbers.angle(
-                checkNumber(MACHINE, 'angle', 0));
+                checkNumber(M, 'angle', 0));
         });
 
     installPrimitiveProcedure(
         'magnitude',
         1,
-        function (MACHINE) {
+        function (M) {
             return baselib.numbers.magnitude(
-                checkNumber(MACHINE, 'magnitude', 0));
+                checkNumber(M, 'magnitude', 0));
         });
 
     installPrimitiveProcedure(
         'conjugate',
         1,
-        function (MACHINE) {
+        function (M) {
             return baselib.numbers.conjugate(
-                checkNumber(MACHINE, 'conjugate', 0));
+                checkNumber(M, 'conjugate', 0));
         });
 
 
@@ -1418,27 +1418,27 @@
     installPrimitiveProcedure(
         'cos',
         1,
-        function (MACHINE) {
+        function (M) {
             return baselib.numbers.cos(
-                checkNumber(MACHINE, 'cos', 0));
+                checkNumber(M, 'cos', 0));
         });
 
 
     installPrimitiveProcedure(
         'cosh',
         1,
-        function (MACHINE) {
+        function (M) {
             return baselib.numbers.cosh(
-                checkNumber(MACHINE, 'cosh', 0));
+                checkNumber(M, 'cosh', 0));
         });
 
     installPrimitiveProcedure(
         'gcd',
         baselib.arity.makeArityAtLeast(1),
-        function (MACHINE) {
+        function (M) {
             var args = [], i, x;
-            for (i = 0; i < MACHINE.argcount; i++) {
-                args.push(checkNumber(MACHINE, 'gcd', i));
+            for (i = 0; i < M.argcount; i++) {
+                args.push(checkNumber(M, 'gcd', i));
             }
             x = args.shift();
             return baselib.numbers.gcd(x, args);
@@ -1447,10 +1447,10 @@
     installPrimitiveProcedure(
         'lcm',
         baselib.arity.makeArityAtLeast(1),
-        function (MACHINE) {
+        function (M) {
             var args = [], i, x;
-            for (i = 0; i < MACHINE.argcount; i++) {
-                args.push(checkNumber(MACHINE, 'lcm', i));
+            for (i = 0; i < M.argcount; i++) {
+                args.push(checkNumber(M, 'lcm', i));
             }
             x = args.shift();
             return baselib.numbers.lcm(x, args);
@@ -1462,43 +1462,43 @@
     installPrimitiveProcedure(
         'exp',
         1,
-        function (MACHINE) {
+        function (M) {
             return baselib.numbers.exp(
-                checkNumber(MACHINE, 'exp', 0));
+                checkNumber(M, 'exp', 0));
         });
 
 
     installPrimitiveProcedure(
         'expt',
         2,
-        function (MACHINE) {
+        function (M) {
             return baselib.numbers.expt(
-                checkNumber(MACHINE, 'expt', 0),
-                checkNumber(MACHINE, 'expt', 1));
+                checkNumber(M, 'expt', 0),
+                checkNumber(M, 'expt', 1));
         });
 
     installPrimitiveProcedure(
         'exact?',
         1,
-        function (MACHINE) {
+        function (M) {
             return baselib.numbers.isExact(
-                checkNumber(MACHINE, 'exact?', 0));
+                checkNumber(M, 'exact?', 0));
         });
 
 
     installPrimitiveProcedure(
         'integer?',
         1,
-        function (MACHINE) {
-            return baselib.numbers.isInteger(MACHINE.env[MACHINE.env.length - 1]);
+        function (M) {
+            return baselib.numbers.isInteger(M.env[M.env.length - 1]);
         });
 
 
     installPrimitiveProcedure(
         'exact-nonnegative-integer?',
         1,
-        function (MACHINE) {
-            return isNatural(MACHINE.env[MACHINE.env.length - 1]);
+        function (M) {
+            return isNatural(M.env[M.env.length - 1]);
         });
 
 
@@ -1506,67 +1506,67 @@
     installPrimitiveProcedure(
         'imag-part',
         1,
-        function (MACHINE) {
+        function (M) {
             return baselib.numbers.imaginaryPart(
-                checkNumber(MACHINE, 'imag-part', 0));
+                checkNumber(M, 'imag-part', 0));
         });
 
 
     installPrimitiveProcedure(
         'real-part',
         1,
-        function (MACHINE) {
+        function (M) {
             return baselib.numbers.realPart(
-                checkNumber(MACHINE, 'real-part', 0));
+                checkNumber(M, 'real-part', 0));
         });
 
 
     installPrimitiveProcedure(
         'make-polar',
         2,
-        function (MACHINE) {
+        function (M) {
             return makeComplexPolar(
-                checkReal(MACHINE, 'make-polar', 0),
-                checkReal(MACHINE, 'make-polar', 1));
+                checkReal(M, 'make-polar', 0),
+                checkReal(M, 'make-polar', 1));
         });
 
 
     installPrimitiveProcedure(
         'make-rectangular',
         2,
-        function (MACHINE) {
+        function (M) {
             return makeComplex(
-                checkReal(MACHINE, 'make-rectangular', 0),
-                checkReal(MACHINE, 'make-rectangular', 1));
+                checkReal(M, 'make-rectangular', 0),
+                checkReal(M, 'make-rectangular', 1));
         });
 
     installPrimitiveProcedure(
         'modulo',
         2,
-        function (MACHINE) {
+        function (M) {
             return baselib.numbers.modulo(
-                checkInteger(MACHINE, 'modulo', 0),
-                checkInteger(MACHINE, 'modulo', 1));
+                checkInteger(M, 'modulo', 0),
+                checkInteger(M, 'modulo', 1));
         });
 
 
     installPrimitiveProcedure(
         'remainder',
         2,
-        function (MACHINE) {
+        function (M) {
             return baselib.numbers.remainder(
-                checkInteger(MACHINE, 'remainder', 0),
-                checkInteger(MACHINE, 'remainder', 1));
+                checkInteger(M, 'remainder', 0),
+                checkInteger(M, 'remainder', 1));
         });
 
 
     installPrimitiveProcedure(
         'quotient',
         2,
-        function (MACHINE) {
+        function (M) {
             return baselib.numbers.quotient(
-                checkInteger(MACHINE, 'quotient', 0),
-                checkInteger(MACHINE, 'quotient', 1));
+                checkInteger(M, 'quotient', 0),
+                checkInteger(M, 'quotient', 1));
         });
 
 
@@ -1574,35 +1574,35 @@
     installPrimitiveProcedure(
         'floor',
         1,
-        function (MACHINE) {
+        function (M) {
             return baselib.numbers.floor(
-                checkReal(MACHINE, 'floor', 0));
+                checkReal(M, 'floor', 0));
         });
     
 
     installPrimitiveProcedure(
         'ceiling',
         1,
-        function (MACHINE) {
+        function (M) {
             return baselib.numbers.ceiling(
-                checkReal(MACHINE, 'ceiling', 0));
+                checkReal(M, 'ceiling', 0));
         });
     
 
     installPrimitiveProcedure(
         'round',
         1,
-        function (MACHINE) {
+        function (M) {
             return baselib.numbers.round(
-                checkReal(MACHINE, 'round', 0));
+                checkReal(M, 'round', 0));
         });
     
 
     installPrimitiveProcedure(
         'truncate',
         1,
-        function (MACHINE) {
-            var n = checkReal(MACHINE, 'truncate', 0);
+        function (M) {
+            var n = checkReal(M, 'truncate', 0);
             if (baselib.numbers.lessThan(n, 0)) {
                 return baselib.numbers.ceiling(n);
             } else {
@@ -1614,36 +1614,36 @@
     installPrimitiveProcedure(
         'numerator',
         1,
-        function (MACHINE) {
+        function (M) {
             return baselib.numbers.numerator(
-                checkRational(MACHINE, 'numerator', 0));
+                checkRational(M, 'numerator', 0));
         });
 
 
     installPrimitiveProcedure(
         'denominator',
         1,
-        function (MACHINE) {
+        function (M) {
             return baselib.numbers.denominator(
-                checkRational(MACHINE, 'denominator', 0));
+                checkRational(M, 'denominator', 0));
         });
 
 
     installPrimitiveProcedure(
         'log',
         1,
-        function (MACHINE) {
+        function (M) {
             return baselib.numbers.log(
-                checkNumber(MACHINE, 'log', 0));
+                checkNumber(M, 'log', 0));
         });
 
 
     installPrimitiveProcedure(
         'sqr',
         1,
-        function (MACHINE) {
+        function (M) {
             return baselib.numbers.sqr(
-                checkNumber(MACHINE, 'sqr', 0));
+                checkNumber(M, 'sqr', 0));
         });
 
 
@@ -1652,9 +1652,9 @@
     installPrimitiveProcedure(
         'sqrt',
         1,
-        function (MACHINE) {
+        function (M) {
             return baselib.numbers.sqrt(
-                checkNumber(MACHINE, 'sqrt', 0));
+                checkNumber(M, 'sqrt', 0));
         });
 
 
@@ -1662,9 +1662,9 @@
     installPrimitiveProcedure(
         'integer-sqrt',
         1,
-        function (MACHINE) {
+        function (M) {
             return baselib.numbers.integerSqrt(
-                checkInteger(MACHINE, 'integer-sqrt', 0));
+                checkInteger(M, 'integer-sqrt', 0));
         });
 
 
@@ -1672,21 +1672,21 @@
     installPrimitiveProcedure(
         'sgn',
         1,
-        function (MACHINE) {
+        function (M) {
             return baselib.numbers.sign(
-                checkInteger(MACHINE, 'sgn', 0));
+                checkInteger(M, 'sgn', 0));
         });
 
 
     installPrimitiveProcedure(
         'min',
         baselib.arity.makeArityAtLeast(1),
-        function(MACHINE) {
+        function(M) {
             var i;
             var next;
-            var currentMin = checkReal(MACHINE, 'min', 0);
-            for (i = 1; i < MACHINE.argcount; i++) {
-                next = checkReal(MACHINE, 'min', i);
+            var currentMin = checkReal(M, 'min', 0);
+            for (i = 1; i < M.argcount; i++) {
+                next = checkReal(M, 'min', i);
                 if (baselib.numbers.lessThan(next, currentMin)) {
                     currentMin = next;
                 }
@@ -1697,12 +1697,12 @@
     installPrimitiveProcedure(
         'max',
         baselib.arity.makeArityAtLeast(1),
-        function(MACHINE) {
+        function(M) {
             var i;
             var next;
-            var currentMax = checkReal(MACHINE, 'min', 0);
-            for (i = 1; i < MACHINE.argcount; i++) {
-                next = checkReal(MACHINE, 'min', i);
+            var currentMax = checkReal(M, 'min', 0);
+            for (i = 1; i < M.argcount; i++) {
+                next = checkReal(M, 'min', i);
                 if (baselib.numbers.greaterThan(next, currentMax)) {
                     currentMax = next;
                 }
@@ -1718,76 +1718,76 @@
     installPrimitiveProcedure(
         'error',
         baselib.arity.makeArityAtLeast(1),
-        function (MACHINE) {
+        function (M) {
 	    var i;
-            if (MACHINE.argcount === 1) {
-                var sym = checkSymbol(MACHINE, 'error', 1);
-                raise(MACHINE, baselib.exceptions.makeExnFail(String(sym), 
-                                                              MACHINE.captureContinuationMarks()));
+            if (M.argcount === 1) {
+                var sym = checkSymbol(M, 'error', 1);
+                raise(M, baselib.exceptions.makeExnFail(String(sym), 
+                                                              M.captureContinuationMarks()));
             } 
             
-            if (isString(MACHINE.env[MACHINE.env.length - 1])) {
+            if (isString(M.env[M.env.length - 1])) {
                 var vs = [];
-                for (i = 1; i < MACHINE.argcount; i++) {
-                    vs.push(baselib.format.format("~e", [MACHINE.env[MACHINE.env.length - 1 - i]]));
+                for (i = 1; i < M.argcount; i++) {
+                    vs.push(baselib.format.format("~e", [M.env[M.env.length - 1 - i]]));
                 }
-                raise(MACHINE, baselib.exceptions.makeExnFail(String(MACHINE.env[MACHINE.env.length - 1]) +
+                raise(M, baselib.exceptions.makeExnFail(String(M.env[M.env.length - 1]) +
                                                               ": " +
                                                               vs.join(' '),
-                                                              MACHINE.captureContinuationMarks()));
+                                                              M.captureContinuationMarks()));
             }
 
-            if (isSymbol(MACHINE.env[MACHINE.env.length - 1])) {
-                var fmtString = checkString(MACHINE, 'error', 1);
-                var args = [MACHINE.env[MACHINE.env.length - 1]];
-                for (i = 2; i < MACHINE.argcount; i++) {
-                    args.push(MACHINE.env[MACHINE.env.length - 1 - i]);
+            if (isSymbol(M.env[M.env.length - 1])) {
+                var fmtString = checkString(M, 'error', 1);
+                var args = [M.env[M.env.length - 1]];
+                for (i = 2; i < M.argcount; i++) {
+                    args.push(M.env[M.env.length - 1 - i]);
                 }
-                raise(MACHINE, baselib.exceptions.makeExnFail(
+                raise(M, baselib.exceptions.makeExnFail(
                     baselib.format.format('~s: ' + String(fmtString),
                                           args),
-                    MACHINE.captureContinuationMarks()));
+                    M.captureContinuationMarks()));
             }
 
             // Fall-through
-            raiseArgumentTypeError(MACHINE, 'error', 'symbol or string', 0, MACHINE.env[MACHINE.env.length - 1]);
+            raiseArgumentTypeError(M, 'error', 'symbol or string', 0, M.env[M.env.length - 1]);
         });
 
 
     installPrimitiveProcedure(
         'raise-mismatch-error',
         3,
-        function (MACHINE) {
-            var name = checkSymbol(MACHINE, 'raise-mismatch-error', 0);
-            var message = checkString(MACHINE, 'raise-mismatch-error', 0);
-            var val = MACHINE.env[MACHINE.env.length - 1 - 2];
-            raise(MACHINE, baselib.exceptions.makeExnFail(
+        function (M) {
+            var name = checkSymbol(M, 'raise-mismatch-error', 0);
+            var message = checkString(M, 'raise-mismatch-error', 0);
+            var val = M.env[M.env.length - 1 - 2];
+            raise(M, baselib.exceptions.makeExnFail(
 		baselib.format.format("~a: ~a~e",
                                       [name,
                                        message,
                                        val]),
-                MACHINE.captureContinuationMarks()));
+                M.captureContinuationMarks()));
         });
 
 
     installPrimitiveProcedure(
         'raise-type-error',
         baselib.arity.makeArityAtLeast(3),
-        function (MACHINE) {
-            var name = checkSymbol(MACHINE, 'raise-type-error', 0);
-            var expected = checkString(MACHINE, 'raise-type-error', 1);
-            if (MACHINE.argcount === 3) {
-                raiseArgumentTypeError(MACHINE, 
+        function (M) {
+            var name = checkSymbol(M, 'raise-type-error', 0);
+            var expected = checkString(M, 'raise-type-error', 1);
+            if (M.argcount === 3) {
+                raiseArgumentTypeError(M, 
                                        name,
                                        expected,
                                        undefined,
-                                       MACHINE.env[MACHINE.env.length - 1 - 2]);
+                                       M.env[M.env.length - 1 - 2]);
             } else {
-                raiseArgumentTypeError(MACHINE, 
+                raiseArgumentTypeError(M, 
                                        name,
                                        expected,
-                                       checkNatural(MACHINE, 'raise-type-error', 2),
-                                       MACHINE.env[MACHINE.env.length - 1 - 2]);
+                                       checkNatural(M, 'raise-type-error', 2),
+                                       M.env[M.env.length - 1 - 2]);
             }
         });
     
@@ -1797,9 +1797,9 @@
     installPrimitiveClosure(
         'make-struct-type',
         makeList(4, 5, 6, 7, 8, 9, 10, 11),
-        function (MACHINE) {
+        function (M) {
             withArguments(
-                MACHINE,
+                M,
                 4,
                 [false, 
                  NULL,
@@ -1839,11 +1839,11 @@
                         makePrimitiveProcedure(
                             constructorName,
                             baselib.numbers.toFixnum(initFieldCount),
-                            function (MACHINE) {
+                            function (M) {
                                 var args = [];
 				var i;
                                 for(i = 0; i < initFieldCount; i++) {
-                                    args.push(MACHINE.env[MACHINE.env.length - 1 - i]);
+                                    args.push(M.env[M.env.length - 1 - i]);
                                 }
                                 return structType.constructor.apply(null, args);
                             });
@@ -1852,18 +1852,18 @@
                         makePrimitiveProcedure(
                             String(name) + "?",
                             1,
-                            function (MACHINE) {
-                                return structType.predicate(MACHINE.env[MACHINE.env.length - 1]);
+                            function (M) {
+                                return structType.predicate(M.env[M.env.length - 1]);
                             });
 
                     var accessorValue = 
                         makePrimitiveProcedure(
                             String(name) + "-accessor",
                             2,
-                            function (MACHINE) {
+                            function (M) {
                                 return structType.accessor(
-                                    MACHINE.env[MACHINE.env.length - 1],
-                                    baselib.numbers.toFixnum(MACHINE.env[MACHINE.env.length - 2]));
+                                    M.env[M.env.length - 1],
+                                    baselib.numbers.toFixnum(M.env[M.env.length - 2]));
                             });
                     accessorValue.structType = structType;
 
@@ -1871,16 +1871,16 @@
                         makePrimitiveProcedure(
                             String(name) + "-mutator",
                             3,
-                            function (MACHINE) {
+                            function (M) {
                                 return structType.mutator(
-                                    MACHINE.env[MACHINE.env.length - 1],
-                                    baselib.numbers.toFixnum(MACHINE.env[MACHINE.env.length - 2]),
-                                    MACHINE.env[MACHINE.env.length - 3]);
+                                    M.env[M.env.length - 1],
+                                    baselib.numbers.toFixnum(M.env[M.env.length - 2]),
+                                    M.env[M.env.length - 3]);
                             });
                     mutatorValue.structType = structType;
 
 
-                    finalizeClosureCall(MACHINE,
+                    finalizeClosureCall(M,
                                         structType,
                                         constructorValue,
                                         predicateValue,
@@ -1893,13 +1893,13 @@
     installPrimitiveProcedure(
         'current-inspector',
         makeList(0, 1),
-        function (MACHINE) {
-            if (MACHINE.argcount === 1) {
-                MACHINE.params['currentInspector'] = 
-                    checkInspector(MACHINE, 'current-inspector', 0);
+        function (M) {
+            if (M.argcount === 1) {
+                M.params['currentInspector'] = 
+                    checkInspector(M, 'current-inspector', 0);
                 return VOID;
             } else {
-                return MACHINE.params['currentInspector'];
+                return M.params['currentInspector'];
             }
         }
     ); 
@@ -1908,12 +1908,12 @@
     installPrimitiveProcedure(
         'make-struct-field-accessor',
         makeList(2, 3),
-        function (MACHINE){
-            var structType = MACHINE.env[MACHINE.env.length - 1].structType;
-            var index = MACHINE.env[MACHINE.env.length - 2];
+        function (M){
+            var structType = M.env[M.env.length - 1].structType;
+            var index = M.env[M.env.length - 2];
             var name;
-            if (MACHINE.argcount === 3) {
-                name = String(MACHINE.env[MACHINE.env.length - 3]);
+            if (M.argcount === 3) {
+                name = String(M.env[M.env.length - 3]);
             } else {
                 name = 'field' + index;
             }
@@ -1922,8 +1922,8 @@
             return makePrimitiveProcedure(
                 name,
                 1,
-                function (MACHINE) {
-                    var aStruct = checkStruct(MACHINE, name, 0);
+                function (M) {
+                    var aStruct = checkStruct(M, name, 0);
                     return structType.accessor(
                         aStruct,
                         baselib.numbers.toFixnum(index));
@@ -1935,12 +1935,12 @@
     installPrimitiveProcedure(
         'make-struct-field-mutator',
         makeList(2, 3),
-        function (MACHINE){
-            var structType = MACHINE.env[MACHINE.env.length - 1].structType;
-            var index = MACHINE.env[MACHINE.env.length - 2];
+        function (M){
+            var structType = M.env[M.env.length - 1].structType;
+            var index = M.env[M.env.length - 2];
             var name;
-            if (MACHINE.argcount === 3) {
-                name = String(MACHINE.env[MACHINE.env.length - 3]);
+            if (M.argcount === 3) {
+                name = String(M.env[M.env.length - 3]);
             } else {
                 name = 'field' + index;
             }
@@ -1949,12 +1949,12 @@
             return makePrimitiveProcedure(
                 name,
                 2,
-                function (MACHINE) {
-                    var aStruct = checkStruct(MACHINE, name, 0);
+                function (M) {
+                    var aStruct = checkStruct(M, name, 0);
                     return structType.mutator(
                         aStruct,
                         baselib.numbers.toFixnum(index),
-                        MACHINE.env[MACHINE.env.length - 2]);
+                        M.env[M.env.length - 2]);
                 });            
         });
 
@@ -1962,8 +1962,8 @@
     installPrimitiveProcedure(
         'make-placeholder',
         1,
-        function(MACHINE) {
-            var v = MACHINE.env[MACHINE.env.length - 1];
+        function(M) {
+            var v = M.env[M.env.length - 1];
             return baselib.placeholders.makePlaceholder(v);
         });
 
@@ -1971,9 +1971,9 @@
     installPrimitiveProcedure(
         'placeholder-set!',
         2,
-        function(MACHINE) {
-            var placeholder = checkPlaceholder(MACHINE, 'placeholder-set!', 0);
-            var val = MACHINE.env[MACHINE.env.length - 2];
+        function(M) {
+            var placeholder = checkPlaceholder(M, 'placeholder-set!', 0);
+            var val = M.env[M.env.length - 2];
             placeholder.set(val);
             return VOID;
         });
@@ -1983,8 +1983,8 @@
     installPrimitiveProcedure(
         'make-reader-graph',
         1,
-        function(MACHINE) {
-            var x = MACHINE.env[MACHINE.env.length - 1];
+        function(M) {
+            var x = M.env[M.env.length - 1];
             return baselib.readergraph.readerGraph(x,
                                                    baselib.hashes.makeLowLevelEqHash(),
                                                    0);
@@ -1996,67 +1996,68 @@
     installPrimitiveProcedure(
         'srcloc',
             5,
-        function(MACHINE) {
-            var source = MACHINE.env[MACHINE.env.length - 1];
-            var line = checkNatural(MACHINE, 'srcloc', 1);
-            var column = checkNatural(MACHINE, 'srcloc', 2);
-            var position = checkNatural(MACHINE, 'srcloc', 3);
-            var span = checkNatural(MACHINE, 'srcloc', 4);
+        function(M) {
+            var source = M.env[M.env.length - 1];
+            var line = checkNatural(M, 'srcloc', 1);
+            var column = checkNatural(M, 'srcloc', 2);
+            var position = checkNatural(M, 'srcloc', 3);
+            var span = checkNatural(M, 'srcloc', 4);
             return baselib.srclocs.makeSrcloc(source, line, column, position, span);
         });
+
     installPrimitiveProcedure(
         'make-srcloc',
         5,
-        function(MACHINE) {
-            var source = MACHINE.env[MACHINE.env.length - 1];
-            var line = checkNatural(MACHINE, 'make-srcloc', 1);
-            var column = checkNatural(MACHINE, 'make-srcloc', 2);
-            var position = checkNatural(MACHINE, 'make-srcloc', 3);
-            var span = checkNatural(MACHINE, 'make-srcloc', 4);
+        function(M) {
+            var source = M.env[M.env.length - 1];
+            var line = checkNatural(M, 'make-srcloc', 1);
+            var column = checkNatural(M, 'make-srcloc', 2);
+            var position = checkNatural(M, 'make-srcloc', 3);
+            var span = checkNatural(M, 'make-srcloc', 4);
             return baselib.srclocs.makeSrcloc(source, line, column, position, span);
         });
+
     installPrimitiveProcedure(
         'srcloc?',
         1,
-        function(MACHINE) {
-            return baselib.srclocs.isSrcloc(MACHINE.env[MACHINE.env.length - 1]);
+        function(M) {
+            return baselib.srclocs.isSrcloc(M.env[M.env.length - 1]);
         });
+
     installPrimitiveProcedure(
         'srcloc-source',
         1,
-        function(MACHINE) {
-            return baselib.srclocs.srclocSource(checkSrcloc(MACHINE, 'srcloc-source', 0));
+        function(M) {
+            return baselib.srclocs.srclocSource(checkSrcloc(M, 'srcloc-source', 0));
         });
+
     installPrimitiveProcedure(
         'srcloc-line',
         1,
-        function(MACHINE) {
-            return baselib.srclocs.srclocLine(checkSrcloc(MACHINE, 'srcloc-line', 0));
+        function(M) {
+            return baselib.srclocs.srclocLine(checkSrcloc(M, 'srcloc-line', 0));
         });
+
     installPrimitiveProcedure(
         'srcloc-column',
         1,
-        function(MACHINE) {
-            return baselib.srclocs.srclocColumn(checkSrcloc(MACHINE, 'srcloc-column', 0));
+        function(M) {
+            return baselib.srclocs.srclocColumn(checkSrcloc(M, 'srcloc-column', 0));
         });
+
     installPrimitiveProcedure(
         'srcloc-position',
         1,
-        function(MACHINE) {
-            return baselib.srclocs.srclocPosition(checkSrcloc(MACHINE, 'srcloc-position', 0));
+        function(M) {
+            return baselib.srclocs.srclocPosition(checkSrcloc(M, 'srcloc-position', 0));
         });
+
     installPrimitiveProcedure(
         'srcloc-span',
         1,
-        function(MACHINE) {
-            return baselib.srclocs.srclocSpan(checkSrcloc(MACHINE, 'srcloc-span', 0));
+        function(M) {
+            return baselib.srclocs.srclocSpan(checkSrcloc(M, 'srcloc-span', 0));
         });
-    
-
-
-
-
-
 
     exports['Primitives'] = Primitives;
     exports['installPrimitiveProcedure'] = installPrimitiveProcedure; 
diff --git a/js-assembler/runtime-src/runtime.js b/js-assembler/runtime-src/runtime.js
index fc7d328..38465ba 100644
--- a/js-assembler/runtime-src/runtime.js
+++ b/js-assembler/runtime-src/runtime.js
@@ -212,11 +212,11 @@
 
     var Machine = function() {
 	this.callsBeforeTrampoline = STACK_LIMIT_ESTIMATE;
-	this.val = undefined;
-	this.proc = undefined;
-	this.argcount = undefined;
-	this.env = [];
-	this.control = [];     // Arrayof (U Frame CallFrame PromptFrame)
+	this.val = undefined;         // value register
+	this.proc = undefined;        // procedure register
+	this.argcount = undefined;    // argument count
+	this.env = [];                // environment
+	this.control = [];            // control: Arrayof (U Frame CallFrame PromptFrame)
 	this.running = false;
 	this.modules = {};     // String -> ModuleRecord
         this.mainModules = []; // Arrayof String
@@ -444,17 +444,16 @@
 
 
     Machine.prototype.trampoline = function(initialJump) {
-	var MACHINE = this;
 	var thunk = initialJump;
 	var startTime = (new Date()).valueOf();
-	MACHINE.callsBeforeTrampoline = STACK_LIMIT_ESTIMATE;
-	MACHINE.params.numBouncesBeforeYield = 
-	    MACHINE.params.maxNumBouncesBeforeYield;
-	MACHINE.running = true;
+	this.callsBeforeTrampoline = STACK_LIMIT_ESTIMATE;
+	this.params.numBouncesBeforeYield = 
+	    this.params.maxNumBouncesBeforeYield;
+	this.running = true;
 
 	while(true) {
             try {
-		thunk(MACHINE);
+		thunk(this);
 		break;
             } catch (e) {
                 // There are a few kinds of things that can get thrown
@@ -479,35 +478,36 @@
                 // The running flag is set to false.
 		if (typeof(e) === 'function') {
                     thunk = e;
-                    MACHINE.callsBeforeTrampoline = STACK_LIMIT_ESTIMATE;
+                    this.callsBeforeTrampoline = STACK_LIMIT_ESTIMATE;
 
-		    if (MACHINE.params.numBouncesBeforeYield-- < 0) {
+		    if (this.params.numBouncesBeforeYield-- < 0) {
 			recomputeMaxNumBouncesBeforeYield(
-			    MACHINE,
+			    this,
 			    (new Date()).valueOf() - startTime);
-			scheduleTrampoline(MACHINE, thunk);
+			scheduleTrampoline(this, thunk);
 			return;
 		    }
 		} else if (e instanceof Pause) {
-                    var restart = makeRestartFunction(MACHINE);
+                    var restart = makeRestartFunction(this);
                     e.onPause(restart);
                     return;
                 } else if (e instanceof HaltError) {
-		    MACHINE.running = false;
-                    e.onHalt(MACHINE);
+		    this.running = false;
+                    e.onHalt(this);
                     return;
                 } else {
 		    // General error condition: just exit out
 		    // of the trampoline and call the current error handler.
-		    MACHINE.running = false;
-                    MACHINE.params.currentErrorHandler(MACHINE, e);
+		    this.running = false;
+                    this.params.currentErrorHandler(this, e);
 	            return;
 		}
             }
 	}
-	MACHINE.running = false;
+	this.running = false;
+        var that = this;
         setTimeout(
-            function() { MACHINE.params.currentSuccessHandler(MACHINE); },
+            function() { that.params.currentSuccessHandler(that); },
             0);
 	return;
     };