Foldable: refactor the documentation

example/foldable/unpack.cpp

@@ -0,0 +1,30 @@
+/*
+@copyright Louis Dionne 2014
+Distributed under the Boost Software License, Version 1.0.
+(See accompanying file LICENSE.md or copy at http://boost.org/LICENSE_1_0.txt)
+ */
+
+#include <boost/hana/functional.hpp>
+#include <boost/hana/list/instance.hpp>
+
+#include <cassert>
+using namespace boost::hana;
+
+
+int main() {
+    //! [main]
+    auto cheap_tie = [](auto& ...vars) {
+        return partial(unpack, [&vars...](auto ...values) {
+            // Using an initializer list sequences the assignments.
+            int dummy[] = {((vars = values), 0)...};
+            (void)dummy;
+        });
+    };
+    int a = 0;
+    char b = '\0';
+    double c = 0;
+
+    cheap_tie(a, b, c)(list(1, '2', 3.3));
+    assert(a == 1 && b == '2' && c == 3.3);
+    //! [main]
+}