X-Git-Url: http://info.iut-bm.univ-fcomte.fr/pub/gitweb/simgrid.git/blobdiff_plain/74950d38bb412bfa1489d8ce0a8c5a194fe87a45..c04b15f5346d042218b4fb8357cace04585e067b:/include/xbt/future.hpp

diff --git a/include/xbt/future.hpp b/include/xbt/future.hpp
index 122d59093b..a374bec117 100644
--- a/include/xbt/future.hpp
+++ b/include/xbt/future.hpp
@@ -9,15 +9,21 @@
 
 #include <cstddef>
 
-#include <utility>
 #include <exception>
+#include <functional>
+#include <stdexcept>
+#include <type_traits>
+#include <utility>
 
 namespace simgrid {
 namespace xbt {
 
-/** A value or an exception
+/** A value or an exception (or nothing)
+ *
+ *  This is similar to `optional<expected<T>>`` but it with a Future/Promise
+ *  like API.
  *
- *  The API is similar to the one of future and promise.
+ *  Also the name is not so great.
  **/
 template<class T>
 class Result {
@@ -112,7 +118,7 @@ public:
 
   /** Extract the value from the future
    *
-   *  After this the value is invalid.
+   *  After this, the value is invalid.
    **/
   T get()
   {
@@ -144,7 +150,7 @@ private:
 };
 
 template<>
-class Result<void> : public Result<nullptr_t>
+class Result<void> : public Result<std::nullptr_t>
 {
 public:
   void set_value()
@@ -153,7 +159,7 @@ public:
   }
   void get()
   {
-    Result<nullptr_t>::get();
+    Result<std::nullptr_t>::get();
   }
 };
 
@@ -171,30 +177,40 @@ public:
   }
 };
 
-/** Fulfill a promise by executing a given code */
+/** Execute some code and set a promise or result accordingly
+ *
+ *  Roughly this does:
+ *
+ *  <pre>
+ *  promise.set_value(code());
+ *  </pre>
+ *
+ *  but it takes care of exceptions and works with `void`.
+ *
+ *  We might need this when working with generic code because
+ *  the trivial implementation does not work with `void` (before C++1z).
+ *
+ *  @param    code  What we want to do
+ *  @param  promise Where to want to store the result
+ */
 template<class R, class F>
 auto fulfillPromise(R& promise, F&& code)
 -> decltype(promise.set_value(code()))
 {
   try {
-    promise.set_value(code());
+    promise.set_value(std::forward<F>(code)());
   }
   catch(...) {
     promise.set_exception(std::current_exception());
   }
 }
 
-/** Fulfill a promise by executing a given code
- *
- *  This is a special version for `std::promise<void>` because the default
- *  version does not compile in this case.
- */
 template<class P, class F>
 auto fulfillPromise(P& promise, F&& code)
 -> decltype(promise.set_value())
 {
   try {
-    (code)();
+    std::forward<F>(code)();
     promise.set_value();
   }
   catch(...) {
@@ -202,6 +218,26 @@ auto fulfillPromise(P& promise, F&& code)
   }
 }
 
+/** Set a promise/result from a future/result
+ *
+ *  Roughly this does:
+ *
+ *  <pre>promise.set_value(future);</pre>
+ *
+ *  but it takes care of exceptions and works with `void`.
+ *
+ *  We might need this when working with generic code because
+ *  the trivial implementation does not work with `void` (before C++1z).
+ *
+ *  @param promise output (a valid future or a result)
+ *  @param future  input (a ready/waitable future or a valid result)
+ */
+template<class P, class F> inline
+void setPromise(P& promise, F&& future)
+{
+  fulfillPromise(promise, [&]{ return std::forward<F>(future).get(); });
+}
+
 }
 }