add original source

source/listing_4.6.cpp

@@ -0,0 +1,16 @@
+#include <future>
+#include <iostream>
+int find_the_answer_to_ltuae()
+{
+    return 42;
+}
+
+void do_other_stuff()
+{}
+
+int main()
+{
+    std::future<int> the_answer=std::async(find_the_answer_to_ltuae);
+    do_other_stuff();
+    std::cout<<"The answer is "<<the_answer.get()<<std::endl;
+}