diff --git a/lib/coffee-script.js b/lib/coffee-script.js
index 00233e76..010fdee9 100644
--- a/lib/coffee-script.js
+++ b/lib/coffee-script.js
@@ -20,7 +20,7 @@
   exports.VERSION = '0.9.1';
   lexer = new Lexer();
   exports.compile = (compile = function(code, options) {
-    options = options || {};
+    options || (options = {});
     try {
       return (parser.parse(lexer.tokenize(code))).compile(options);
     } catch (err) {
diff --git a/lib/command.js b/lib/command.js
index c646c36c..21f37060 100644
--- a/lib/command.js
+++ b/lib/command.js
@@ -220,7 +220,7 @@
     var o;
     optionParser = new optparse.OptionParser(SWITCHES, BANNER);
     o = (options = optionParser.parse(process.argv.slice(2, process.argv.length)));
-    options.compile = options.compile || (!!o.output);
+    options.compile || (options.compile = (!!o.output));
     options.run = !(o.compile || o.print || o.lint);
     options.print = !!(o.print || (o.eval || o.stdio && o.compile));
     return (sources = options.arguments);
diff --git a/lib/lexer.js b/lib/lexer.js
index bc10477b..c5c04538 100644
--- a/lib/lexer.js
+++ b/lib/lexer.js
@@ -324,7 +324,7 @@
       if (value && value.match(CODE)) {
         this.tagParameters();
       }
-      value = value || this.chunk.substr(0, 1);
+      value || (value = this.chunk.substr(0, 1));
       this.i += value.length;
       spaced = this.prev() && this.prev().spaced;
       tag = value;
@@ -435,7 +435,7 @@
     };
     Lexer.prototype.balancedString = function(str, delimited, options) {
       var _d, _e, _f, _g, close, i, levels, open, pair, slash;
-      options = options || {};
+      options || (options = {});
       slash = delimited[0][0] === '/';
       levels = [];
       i = 0;
@@ -478,7 +478,7 @@
     };
     Lexer.prototype.interpolateString = function(str, options) {
       var _d, _e, _f, _g, _h, _i, escaped, expr, i, idx, inner, interpolated, lexer, nested, pi, quote, tag, tok, token, tokens, value;
-      options = options || {};
+      options || (options = {});
       if (str.length < 3 || !starts(str, '"')) {
         return this.token('STRING', str);
       } else {
diff --git a/lib/nodes.js b/lib/nodes.js
index c8086c79..ed2783cf 100644
--- a/lib/nodes.js
+++ b/lib/nodes.js
@@ -48,7 +48,7 @@
     };
     BaseNode.prototype.compileReference = function(o, options) {
       var compiled, pair, reference;
-      options = options || {};
+      options || (options = {});
       pair = (function() {
         if (!((this instanceof CallNode || this.contains(function(n) {
           return n instanceof CallNode;
@@ -105,7 +105,7 @@
     };
     BaseNode.prototype.toString = function(idt, override) {
       var _b, _c, _d, _e, child, children;
-      idt = idt || '';
+      idt || (idt = '');
       children = (function() {
         _b = []; _d = this.collectChildren();
         for (_c = 0, _e = _d.length; _c < _e; _c++) {
@@ -207,7 +207,7 @@
       return this;
     };
     Expressions.prototype.compile = function(o) {
-      o = o || {};
+      o || (o = {});
       return o.scope ? Expressions.__superClass__.compile.call(this, o) : this.compileRoot(o);
     };
     Expressions.prototype.compileNode = function(o) {
@@ -318,7 +318,7 @@
     ValueNode = function(_b, _c) {
       this.properties = _c;
       this.base = _b;
-      this.properties = this.properties || [];
+      this.properties || (this.properties = []);
       return this;
     };
     __extends(ValueNode, BaseNode);
@@ -382,7 +382,7 @@
       only = del(o, 'onlyFirst');
       op = del(o, 'operation');
       props = only ? this.properties.slice(0, this.properties.length - 1) : this.properties;
-      o.chainRoot = o.chainRoot || this;
+      o.chainRoot || (o.chainRoot = this);
       if (this.parenthetical && !props.length) {
         this.base.parenthetical = true;
       }
@@ -445,7 +445,7 @@
       this.isNew = false;
       this.isSuper = variable === 'super';
       this.variable = this.isSuper ? null : variable;
-      this.args = this.args || [];
+      this.args || (this.args = []);
       this.compileSplatArguments = function(o) {
         return SplatNode.compileSplattedArray.call(this, this.args, o);
       };
@@ -552,7 +552,7 @@
     AccessorNode.prototype.compileNode = function(o) {
       var name, namePart;
       name = this.name.compile(o);
-      o.chainRoot.wrapped = o.chainRoot.wrapped || this.soakNode;
+      o.chainRoot.wrapped || (o.chainRoot.wrapped = this.soakNode);
       namePart = name.match(IS_STRING) ? ("[" + (name) + "]") : ("." + (name));
       return this.prototype + namePart;
     };
@@ -568,7 +568,7 @@
     IndexNode.prototype.children = ['index'];
     IndexNode.prototype.compileNode = function(o) {
       var idx, prefix;
-      o.chainRoot.wrapped = o.chainRoot.wrapped || this.soakNode;
+      o.chainRoot.wrapped || (o.chainRoot.wrapped = this.soakNode);
       idx = this.index.compile(o);
       prefix = this.proto ? '.prototype' : '';
       return "" + (prefix) + "[" + (idx) + "]";
@@ -637,7 +637,7 @@
       to = _b[1];
       idx = del(o, 'index');
       step = del(o, 'step');
-      step = step && ("" + (idx) + " += " + (step.compile(o)));
+      step && (step = ("" + (idx) + " += " + (step.compile(o))));
       return from <= to ? ("" + (idx) + " = " + (from) + "; " + (idx) + " <" + (this.equals) + " " + (to) + "; " + (step || ("" + (idx) + "++"))) : ("" + (idx) + " = " + (from) + "; " + (idx) + " >" + (this.equals) + " " + (to) + "; " + (step || ("" + (idx) + "--")));
     };
     RangeNode.prototype.compileArray = function(o) {
@@ -745,7 +745,7 @@
   exports.ArrayNode = (function() {
     ArrayNode = function(_b) {
       this.objects = _b;
-      this.objects = this.objects || [];
+      this.objects || (this.objects = []);
       this.compileSplatLiteral = function(o) {
         return SplatNode.compileSplattedArray.call(this, this.objects, o);
       };
@@ -782,7 +782,7 @@
       this.properties = _d;
       this.parent = _c;
       this.variable = _b;
-      this.properties = this.properties || [];
+      this.properties || (this.properties = []);
       this.returns = false;
       return this;
     };
@@ -832,8 +832,8 @@
         }
         if (func instanceof CodeNode && func.bound) {
           func.bound = false;
-          constScope = constScope || new Scope(o.scope, constructor.body, constructor);
-          me = me || constScope.freeVariable();
+          constScope || (constScope = new Scope(o.scope, constructor.body, constructor));
+          me || (me = constScope.freeVariable());
           pname = pvar.compile(o);
           if (constructor.body.empty()) {
             constructor.body.push(new ReturnNode(literal('this')));
@@ -982,8 +982,8 @@
     CodeNode = function(_b, _c, tag) {
       this.body = _c;
       this.params = _b;
-      this.params = this.params || [];
-      this.body = this.body || new Expressions();
+      this.params || (this.params = []);
+      this.body || (this.body = new Expressions());
       this.bound = tag === 'boundfunc';
       return this;
     };
@@ -1064,7 +1064,7 @@
     };
     CodeNode.prototype.toString = function(idt) {
       var _b, _c, _d, _e, child, children;
-      idt = idt || '';
+      idt || (idt = '');
       children = (function() {
         _b = []; _d = this.collectChildren();
         for (_c = 0, _e = _d.length; _c < _e; _c++) {
@@ -1314,7 +1314,7 @@
       if (this.operator === '?=') {
         return ("" + (first) + " = " + (ExistenceNode.compileTest(o, literal(firstVar))[0]) + " ? " + (firstVar) + " : " + (second));
       }
-      return "" + (first) + " = " + (firstVar) + " " + (this.operator.substr(0, 2)) + " " + (second);
+      return "" + (first) + " " + (this.operator.substr(0, 2)) + " (" + (firstVar) + " = " + (second) + ")";
     };
     OpNode.prototype.compileExistence = function(o) {
       var _b, ref, test;
@@ -1495,7 +1495,7 @@
       this.index = _d;
       this.name = _c;
       this.body = _b;
-      this.index = this.index || null;
+      this.index || (this.index = null);
       this.source = source.source;
       this.guard = source.guard;
       this.step = source.step;
@@ -1635,7 +1635,7 @@
       this.tags = _d;
       this.body = _c;
       this.condition = _b;
-      this.tags = this.tags || {};
+      this.tags || (this.tags = {});
       if (this.tags.invert) {
         this.condition = new OpNode('!', new ParentheticalNode(this.condition));
       }
@@ -1700,7 +1700,7 @@
       return this;
     };
     IfNode.prototype.isStatement = function(o) {
-      return this.statement = this.statement || (!!((o && o.top) || this.tags.statement || this.bodyNode().isStatement(o) || (this.elseBody && this.elseBodyNode().isStatement(o))));
+      return this.statement || (this.statement = (!!((o && o.top) || this.tags.statement || this.bodyNode().isStatement(o) || (this.elseBody && this.elseBodyNode().isStatement(o)))));
     };
     IfNode.prototype.compileCondition = function(o) {
       var _b, _c, _d, _e, cond, conditions;
@@ -1722,8 +1722,8 @@
     };
     IfNode.prototype.makeReturn = function() {
       if (this.isStatement()) {
-        this.body = this.body && this.ensureExpressions(this.body.makeReturn());
-        this.elseBody = this.elseBody && this.ensureExpressions(this.elseBody.makeReturn());
+        this.body && (this.body = this.ensureExpressions(this.body.makeReturn()));
+        this.elseBody && (this.elseBody = this.ensureExpressions(this.elseBody.makeReturn()));
         return this;
       } else {
         return new ReturnNode(this);
diff --git a/lib/optparse.js b/lib/optparse.js
index c94e9f48..94eb6079 100755
--- a/lib/optparse.js
+++ b/lib/optparse.js
@@ -83,7 +83,7 @@
     var match;
     match = longFlag.match(OPTIONAL);
     longFlag = longFlag.match(LONG_FLAG)[1];
-    options = options || {};
+    options || (options = {});
     return {
       name: longFlag.substr(2),
       shortFlag: shortFlag,
diff --git a/lib/rewriter.js b/lib/rewriter.js
index 7245e11f..f0ae8b45 100644
--- a/lib/rewriter.js
+++ b/lib/rewriter.js
@@ -264,7 +264,7 @@
           _f = pair;
           open = _f[0];
           close = _f[1];
-          levels[open] = levels[open] || 0;
+          levels[open] || (levels[open] = 0);
           if (token[0] === open) {
             if (levels[open] === 0) {
               openLine[open] = token[2];
diff --git a/src/nodes.coffee b/src/nodes.coffee
index 15ce8d17..526f86a2 100644
--- a/src/nodes.coffee
+++ b/src/nodes.coffee
@@ -1121,7 +1121,7 @@ exports.OpNode = class OpNode extends BaseNode
     second = "(#{second})" if @second instanceof OpNode
     o.scope.find(first) if first.match(IDENTIFIER)
     return "#{first} = #{ ExistenceNode.compileTest(o, literal(firstVar))[0] } ? #{firstVar} : #{second}" if @operator is '?='
-    "#{first} = #{firstVar} #{ @operator.substr(0, 2) } #{second}"
+    "#{first} #{ @operator.substr(0, 2) } (#{firstVar} = #{second})"
 
   # If this is an existence operator, we delegate to `ExistenceNode.compileTest`
   # to give us the safe references for the variables.