Extended annotate to handle printing

src/lectures/annotate.clj

@@ -20,31 +20,56 @@
       (eval '(do
                (ns lectures.sandbox)
                (def placeholder-values (atom {}))
+               (def placeholder-outputs (atom {}))
                (defmacro store-result [number & body]
                  `(try
-                    (let [value# (do ~@body)]
-                      (swap! ~'lectures.sandbox/placeholder-values assoc ~number value#)
-                      value#)
+                    (let [output# (new java.io.StringWriter)]
+                      (binding [*out* output#]
+                        (let [value# (do ~@body)]
+
+                          (swap! ~'lectures.sandbox/placeholder-values assoc ~number value#)
+                          (swap! ~'lectures.sandbox/placeholder-outputs
+                                 assoc ~number (str output#))
+                          value#)))
                     (catch Throwable e#
                       (swap! ~'lectures.sandbox/placeholder-values assoc ~number e#)
                       nil)))))
       (eval (read-string code)))
-    (let [result (eval '@lectures.sandbox/placeholder-values)]
+    (let [result (eval '@lectures.sandbox/placeholder-values)
+          outputs (eval '@lectures.sandbox/placeholder-outputs)]
       (remove-ns 'lectures.sandbox)
-      result)))
+      {:values result, :outputs outputs})))
 
 (defn- placeholder->str
   [value]
   (condp instance? value
     Throwable (str (-> value class .getName) ": " (.getMessage value))
     (pr-str value)))
 
+(defn- prettify-output
+  [output]
+  (->> output
+       str/split-lines
+       (map (partial str "; "))
+       (str/join "\n")
+       (str ";; OUTPUT:\n")))
+
+
 (defn- replace-placeholders
-  [code placeholders]
-  (str/replace code #"(?m)\{(\d+)\}$" #(-> % second Integer. placeholders placeholder->str)))
+  [code placeholders outputs]
+  (str/replace code #"(?m)\{(\d+)\}$"
+    (fn [[_ match]]
+      (let [id (Integer. match)
+            value-string (-> id
+                             placeholders
+                             placeholder->str)
+            output (outputs id)]
+        (if (not-empty output)
+          (str value-string "\n" (prettify-output output))
+          value-string)))))
 
 (defn annotate
   [code]
   (let [code (assign-placeholders code)
-        values (eval-placeholders code)]
-    (replace-placeholders code values)))
+        {:keys [values outputs]} (eval-placeholders code)]
+    (replace-placeholders code values outputs)))