fixes #835 (#1022)

Author: martin-henz

xml/chapter3/section3/subsection3.xml

@@ -666,6 +666,52 @@ const put = operation_table("insert");
     </SPLITINLINE>
     for a local table.
     <LABEL NAME="ex:numeric-keys"/>
+    <SOLUTION>
+      <SNIPPET>
+	<JAVASCRIPT>
+// Solution by GitHub user clean99
+
+function make_table(same_key) {
+    const local_table = list("*table*");
+    function assoc(key, records) {
+        return is_null(records)
+               ? undefined
+               : same_key(key, head(head(records)))
+               ? head(records)
+               : assoc(key, tail(records));
+    }
+    function lookup(key) {
+        const record = assoc(key, tail(local_table));
+        return is_undefined(record)
+               ? undefined
+               : tail(record);
+    }
+    function insert(key, value) {
+        const record = assoc(key, tail(local_table));
+        if (is_undefined(record)) {
+               set_tail(local_table,
+                        pair(pair(key, value), tail(local_table)));
+            } else {
+               set_tail(record, value);
+            }
+            return "ok";
+    }
+    function dispatch(m) {
+        return m === "lookup"
+               ? lookup
+               : m === "insert"
+               ? insert
+               : error(m, "unknow operation -- table");
+    }
+    return dispatch;
+}
+
+const operation_table = make_table((a, b) => a === b);
+const get = operation_table("lookup");
+const put = operation_table("insert");
+	</JAVASCRIPT>
+      </SNIPPET>
+    </SOLUTION>
   </EXERCISE>
 
   <EXERCISE>