Factor show out to its own package.

src/ludus/prelude.clj

@@ -1,6 +1,7 @@
 (ns ludus.prelude
   (:require
-   [ludus.data :as data]))
+   [ludus.data :as data]
+   [ludus.show]))
 
 (def eq {:name "eq"
          ::data/type ::data/clj
@@ -44,6 +45,17 @@
                     (println (apply str args))
                     :ok)})
 
+(declare show)
+
+(defn- show-vector [v]
+  (if (= (first v) ::data/tuple)
+    (str "(" (apply str (into [] (comp (map (:body show)) (interpose ", ")) (next v))) ")")
+    (str "[" (apply str (into [] (comp (map (:body show)) (interpose ", ")) v)) "]")))
+
+(def show {:name "show"
+  ::data/type ::data/clj
+  :body ludus.show/show})
+
 (def prelude {"eq" eq
               "add" add
               "panic!" panic!
@@ -53,4 +65,5 @@
               "div" div
               "inc" inc-
               "dec" dec-
-              "not" not})
+              "not" not
+              "show" show})

src/ludus/show.clj

@@ -0,0 +1,54 @@
+(ns ludus.show
+  (:require
+    [ludus.data :as data]
+    [clojure.pprint :as pp]))
+
+(declare show show-linear show-keyed)
+
+(defn- show-vector [v]
+  (if (= (first v) ::data/tuple)
+    (str "(" (apply str (into [] show-linear (next v))) ")")
+    (str "[" (apply str (into [] show-linear v)) "]")))
+
+;; TODO: 
+(defn- show-map [v]
+  (cond
+  	(or (= (::data/type v) ::data/fn)
+  		(= (::data/type v) ::data/clj))
+	(str "fn " (:name v))
+
+    (= (::data/type v) ::data/ns)
+    (str "ns " (::data/name v) " {"
+    	(apply str (into [] show-keyed (dissoc v ::data/struct ::data/type ::data/name)))
+    	"}")
+
+    (::data/struct v) 
+    (str "@{" (apply str (into [] show-keyed (dissoc v ::data/struct))) "}")
+
+    :else
+    (str "#{" (apply str (into [] show-keyed v)) "}")
+
+    ))
+
+(defn- show-set [v]
+  (str "${" (apply str (into [] show-linear v)) "}"))
+
+(defn show [v]
+  (cond
+    (string? v) (str "\"" v "\"")
+    (number? v) (str v)
+    (keyword? v) (str v)
+    (boolean? v) (str v)
+    (nil? v) "nil"
+    (vector? v) (show-vector v)
+    (set? v) (show-set v)
+    (map? v) (show-map v)
+    :else (with-out-str (pp/pprint v))))
+
+(def show-linear (comp (map show) (interpose ", ")))
+
+(def show-keyed (comp 
+                  (map #(str (show (first %)) " " (show (second %))))
+                  (interpose ", ")))
+
+(show {::data/type ::data/fn :name "foo"})