diff --git a/src/parser.mly b/src/parser.mly
index 66954c6..529a795 100644
--- a/src/parser.mly
+++ b/src/parser.mly
@@ -136,7 +136,7 @@ exp:
 | simple_exp DOT LPAREN exp RPAREN LESS_MINUS exp { Put($1, $4, $7) }
 | simple_exp DOT IDENT LESS_MINUS exp { Put($1, Str $3, $5) }
 | simple_exp COLON_EQUAL exp { Put($1, Str "ref", $3) }
-| exp SEMICOLON exp { Let(Syntax.gentmp (), $1, $3) }
+| exp SEMICOLON exp { Let("", $1, $3) }
 | ARRAY_CREATE simple_exp simple_exp %prec prec_app { Array($2, $3) }
 | error
     { failwith
diff --git a/src2/parser.ml b/src2/parser.ml
index 8b64024..408122f 100644
--- a/src2/parser.ml
+++ b/src2/parser.ml
@@ -18,7 +18,7 @@ let ident i = i |> (
   ((skip >> (range 'a' 'z' <|> nstr "_") <~> rep(range 'A' 'Z' <|>range 'a' 'z' <|> range '0' '9' <|> nstr "_") ) >>>(fun (a,b)->String.concat "" (a::b)))
   >>> (fun (a,b)->a^b))
   >?> (function
-    | "_" -> genid ""
+    | "_" -> ""
     | a when not(List.mem a keywords) -> a
     | _ -> failwith "error"
   )
@@ -84,7 +84,7 @@ and fields i = i |> (
 and exp i = i |> (
   (_let <~> rep(str ";" >> _let) >>> (fun (a, bs) ->
     List.fold_left (fun a b ->
-      Let(genid "", a, b)
+      Let("", a, b)
     ) a bs
   ))
 )
diff --git a/src3/emit.ml b/src3/emit.ml
index b92cf31..b398606 100644
--- a/src3/emit.ml
+++ b/src3/emit.ml
@@ -28,6 +28,7 @@ let rec o_j fp = function
   | JGet(e1,e2) -> Format.fprintf fp "%a[%a]" o_j e1 o_j e2
   | JPut(e1,e2,e3) -> Format.fprintf fp "%a[%a]=%a" o_j e1 o_j e2 o_j e3
   | JPre(op,e1) -> Format.fprintf fp "(%s %a)" op o_j e1
+  | JApp(e,[JUndefined]) -> Format.fprintf fp "%a()" o_j e
   | JApp(e,es) -> Format.fprintf fp "%a(%a)" o_j e o_js es
   | JIf(e1,e2,e3) -> Format.fprintf fp "(%a ? %a : %a)" o_j e1 o_j e2 o_j e3
   | JFun(is, s) -> Format.fprintf fp "(function(%a){%a})" o_is is o_s s
@@ -43,10 +44,18 @@ and o_ijs fp js =
   Format.fprintf fp "%a@?" (os o_ij) js
 
 and o_s fp = function
+  | SVar(i,JVar j) when i = j -> ()
+  | SVar("",JVar j) -> ()
+  | SVar("",j) -> Format.fprintf fp "%a;" o_j j
   | SVar(i,j) -> Format.fprintf fp "var %s = %a;" i o_j j
+  | SDef("") -> ()
   | SDef(i) -> Format.fprintf fp "var %s;" i
+  | SAssign(i,JVar j) when i = j -> ()
+  | SAssign("",JVar j) -> ()
+  | SAssign("",j) -> Format.fprintf fp "%a;" o_j j
   | SAssign(i,j) -> Format.fprintf fp "%s = %a;" i o_j j
   | SExp(j) -> Format.fprintf fp "%a;" o_j j
+  | SRet(JUndefined) -> Format.fprintf fp "return;"
   | SRet(j) -> Format.fprintf fp "return %a;" o_j j
   | SIf(j,s1, s2) -> Format.fprintf fp "if(%a) %a else %a" o_j j o_s2 s1 o_s2 s2
   | SFun(i,is, s) -> Format.fprintf fp "function %s(%a) {%a}" i o_is is o_s s
diff --git a/src3/inline.ml b/src3/inline.ml
index 3ff299b..a27c127 100644
--- a/src3/inline.ml
+++ b/src3/inline.ml
@@ -22,7 +22,7 @@ let inline env (zs,e) (ys:e list) =
       let (zs,e) = List.fold_right2 (fun z y (zs, e) ->
         match y with
         | Var n -> ((z,n)::zs, e)
-        | _ -> let i = genid "z" in ((z,i)::zs, Let(i, y, e))
+        | _ -> let i = gentmp() in ((z,i)::zs, Let(i, y, e))
       ) zs ys ([],e) in
 
       Alpha.g zs e
diff --git a/src3/javascript.ml b/src3/javascript.ml
index 7007a78..bee8ac4 100644
--- a/src3/javascript.ml
+++ b/src3/javascript.ml
@@ -79,7 +79,12 @@ let (@@) a b =
   if a = SNil then b else
   if b = SNil then a else SCons(a,b)
 
-let rec cnve = function
+type r =
+| RRet
+| RExp
+| RVar of string
+
+let rec cnve tl = function
   | Int(i) -> SNil,JInt(i)
   | Float(i) -> SNil,JFloat(i)
   | Var(i) -> SNil,JVar(i)
@@ -88,73 +93,80 @@ let rec cnve = function
   | Bool(i) -> SNil,JBool(i)
   | Unit -> SNil,JUndefined
   | Bin(e1,op,e2) ->
-    let s1,j1 = cnve e1 in
-    let s2,j2 = cnve e2 in
+    let s1,j1 = cnve tl e1 in
+    let s2,j2 = cnve tl e2 in
     s1 @@ s2, JBin(j1, op, j2)
   | Get(e1,e2) ->
-    let s1,j1 = cnve e1 in
-    let s2,j2 = cnve e2 in
+    let s1,j1 = cnve tl e1 in
+    let s2,j2 = cnve tl e2 in
     s1 @@ s2, JGet(j1, j2)
   | Put(e1,e2,e3) ->
-    let s1,j1 = cnve e1 in
-    let s2,j2 = cnve e2 in
-    let s3,j3 = cnve e3 in
+    let s1,j1 = cnve tl e1 in
+    let s2,j2 = cnve tl e2 in
+    let s3,j3 = cnve tl e3 in
     s1 @@ s2 @@ s3, JPut(j1, j2, j3)
   | Pre(op,e1) ->
-    let s1,j1 = cnve e1 in
+    let s1,j1 = cnve tl e1 in
     s1, JPre(op, j1)
   | App(e,es) ->
-    let s,j = cnve e in
+    let s,j = cnve tl e in
     let ss,js = List.fold_right (fun e (ls,es) ->
-      let l,e = cnve e in
+      let l,e = cnve tl e in
       l @@ ls, (e::es)
     ) es (SNil,[]) in
     s @@ ss, JApp(j, js)
-  | If(e1,e2,e3) ->
-    let s1,j1 = cnve e1 in
-    let s2,j2 = cnve e2 in
-    let s3,j3 = cnve e3 in
-    let i = genid "tmp" in
-    SDef(i) @@ s1 @@ SIf(j1, s2 @@ SAssign(i,j2), s3 @@ SAssign(i,j3)), JVar(i)
   | Let(i,e1,e2) ->
-    let s1, j1 = cnve e1 in
-    let s2, j2 = cnve e2 in
+    let s1, j1 = cnve tl e1 in
+    let s2, j2 = cnve tl e2 in
     s1 @@ SVar(i, j1) @@ s2, j2
   | LetRec(i, Fun(is, e1), e2) ->
-    let s1 = cnv true e1 in
-    let s2, j2 = cnve e2 in
+    let s1 = cnv RRet e1 in
+    let s2, j2 = cnve tl e2 in
     SFun(i, is, s1) @@ s2, j2
 
   | Fun(is, e1) ->
-    let s1 = cnv true e1 in
+    let s1 = cnv RRet e1 in
     SNil, JFun(is, s1)
   | Rec(ies) ->
 
     let ss,js = List.fold_right (fun (i,e) (ls,es) ->
-      let l,e = cnve e in
+      let l,e = cnve tl e in
       l @@ ls, ((i,e)::es)
     ) ies (SNil,[]) in
     ss,JRec(js)
-
+  | If(e1,e2,e3) ->
+    begin match tl with
+    | RVar i ->
+      let s1,j1 = cnve RExp e1 in
+      let s2,j2 = cnve tl e2 in
+      let s3,j3 = cnve tl e3 in
+      s1 @@ SIf(j1, s2 @@ SAssign(i,j2), s3 @@ SAssign(i,j3)), JVar(i)
+    | _ ->
+      let s1,j1 = cnve RExp e1 in
+      let s2,j2 = cnve tl e2 in
+      let s3,j3 = cnve tl e3 in
+      let i = gentmp () in
+      SDef(i) @@ s1 @@ SIf(j1, s2 @@ SAssign(i,j2), s3 @@ SAssign(i,j3)), JVar(i)
+    end
   | e -> Format.fprintf Format.std_formatter "error %a@." show_e e; assert false
 
 and cnv tl = function
   | Let(i,e1,e2) ->
-    let s1, j1 = cnve e1 in
-    s1 @@ SVar(i, j1) @@ cnv tl e2
+    let s1, j1 = cnve (RVar i) e1 in
+    begin match s1 with
+    | SNil -> SVar(i, j1) @@ cnv tl e2
+    | _ -> SDef(i) @@ s1 @@ SAssign(i, j1) @@ cnv tl e2
+    end
   | LetRec(i, Fun(is, e1), e2) ->
-    let s1 = cnv true e1 in
+    let s1 = cnv RRet e1 in
     SFun(i, is, s1) @@ cnv tl e2
-  | If(e1, e2, e3) when tl ->
-    let s1, j1 = cnve e1 in
-    let s2 = cnv true e2 in
-    let s3 = cnv true e3 in
+  | If(e1, e2, e3) when tl=RRet ->
+    let s1, j1 = cnve RExp e1 in
+    let s2 = cnv RRet e2 in
+    let s3 = cnv RRet e3 in
     s1 @@ SIf(j1, s2, s3)
-  | e when tl ->
-    let s, j = cnve e in
-    s @@ SRet j
   | e ->
-    let s, j = cnve e in
-    s @@ SExp j
+    let s, j = cnve RExp e in
+    s @@ (match tl with RRet -> SRet j | _ -> SExp j)
 
-let f e = cnv false e
+let f e = cnv RExp e