diff --git a/lib/dune b/lib/dune
index dd2f8c1..fc4888e 100644
--- a/lib/dune
+++ b/lib/dune
@@ -1,5 +1,6 @@
 (library
- (name spice))
+ (name spice)
+ (libraries fmt))
 
 (menhir
  (modules parser)
diff --git a/lib/syn.ml b/lib/syn.ml
index cbfba2c..5878076 100644
--- a/lib/syn.ml
+++ b/lib/syn.ml
@@ -66,31 +66,25 @@ let string_of_binop = function
   | Grt_eql -> ">="
   | Lst_eql -> "<="
 
-let pf = Format.fprintf
-let pp_str ppf str = pf ppf "%S" str
-
 let pp_list pp_ele ppf list =
-  pf ppf "[";
+  Fmt.pf ppf "[";
   List.iteri
     (fun i ele ->
-      if i > 0 then pf ppf ",";
+      if i > 0 then Fmt.pf ppf ",";
       pp_ele ppf ele)
     list;
-  pf ppf "]"
+  Fmt.pf ppf "]"
 
 let rec pp_exp ppf = function
-  | Literal (Int n) -> pf ppf "{\"int\":%s}" (Int64.to_string n)
-  | Literal l -> pf ppf "%s" (string_of_literal l)
-  | Path (Var x) -> pf ppf "{\"var\":%S}" x
-  | Path (Ele (e, x)) -> pf ppf "{\"ele\":%a,\"field\":%S}" pp_exp e x
-  | Call (fn, args) -> pf ppf "{\"call\":%a}" (pp_list pp_exp) (Path fn :: args)
+  | Literal (Int n) -> Fmt.pf ppf "{\"int\":%s}" (Int64.to_string n)
+  | Literal l -> Fmt.pf ppf "%s" (string_of_literal l)
+  | Path (Var x) -> Fmt.pf ppf "{\"var\":%S}" x
+  | Path (Ele (e, x)) -> Fmt.pf ppf "{\"ele\":%a,\"field\":%S}" pp_exp e x
+  | Call (fn, args) -> Fmt.pf ppf "{\"call\":%a}" (pp_list pp_exp) (Path fn :: args)
   | If (ec, et, ee) ->
-      pf ppf "{\"if\":%a,\"then\":%a,\"else\":%a}"
-        pp_exp ec
-        pp_exp et
-        pp_exp ee
+      Fmt.pf ppf "{\"if\":%a,\"then\":%a,\"else\":%a}" pp_exp ec pp_exp et pp_exp ee
   | Binop (op, e1, e2) ->
-      pf
+      Fmt.pf
         ppf
         "{\"binop\":%S,\"lhs\":%a,\"rhs\":%a}"
         (string_of_binop op)
@@ -99,22 +93,23 @@ let rec pp_exp ppf = function
         pp_exp
         e2
   | Fun (params, body) ->
-      pf ppf "{\"fun\":%a,\"body\":%a}" (pp_list pp_str) params pp_exp body
-  | Obj body -> pf ppf "{\"obj\":%a}" (pp_list pp_item) body
-  | Scope body -> pf ppf "{\"scope\":%a}" (pp_list pp_item) body
+      Fmt.pf ppf "{\"fun\":%a,\"body\":%a}" (pp_list Fmt.string) params pp_exp body
+  | Obj body -> Fmt.pf ppf "{\"obj\":%a}" (pp_list pp_item) body
+  | Scope body -> Fmt.pf ppf "{\"scope\":%a}" (pp_list pp_item) body
 
 and pp_item ppf = function
-  | Item_exp e -> pf ppf "{\"exp\":%a}" pp_exp e
-  | Item_val (name, rhs) -> pf ppf "{\"val\":%S,\"rhs\":%a}" name pp_exp rhs
+  | Item_exp e -> Fmt.pf ppf "{\"exp\":%a}" pp_exp e
+  | Item_val (name, rhs) -> Fmt.pf ppf "{\"val\":%S,\"rhs\":%a}" name pp_exp rhs
   | Item_fun (name, params, body) ->
-      pf
+      Fmt.pf
         ppf
         "{\"fun\":%S,\"params\":%a,\"body\":%a}"
         name
-        (pp_list pp_str)
+        (pp_list Fmt.string)
         params
         pp_exp
         body
-  | Item_obj (name, body) -> pf ppf "{\"obj\":%S,\"body\":%a}" name (pp_list pp_item) body
+  | Item_obj (name, body) ->
+      Fmt.pf ppf "{\"obj\":%S,\"body\":%a}" name (pp_list pp_item) body
 
 let pp_modl ppf m = pp_list pp_item ppf m.items