Fixes to futures (#505)

* Fixes to futures

Fixed unnecessary copies of copyable result types when futures are used as rvalues.
Propagating exceptions for move-only types are now scheduled on the executor (I'm not sure why they were not scheduled before).
Added `copy()` algorithm to utility.hpp to explicitly copy objects.

* Forwarding lambdas need to be mutable.

* Filling in missing documentation and fixing some includes.

* Adding unit test for utility.hpp

* Taking my more refined implementation of copy from artemis

Author: sean-parent

docs/libraries/concurrency/future.hpp/packaged_task3CArgs3E/m_canceled.md

@@ -0,0 +1,14 @@
+---
+layout: method
+title: canceled
+owner: sean-parent
+brief: Returns true if there are no longer any futures attached to the task.
+tags:
+  - method
+defined_in_file: concurrency/future.hpp
+overloads:
+  bool canceled() const:
+    description: __OPTIONAL__
+    return: __OPTIONAL__
+    signature_with_names: bool canceled() const
+---

docs/libraries/utility.hpp/f_copy.md

@@ -0,0 +1,32 @@
+---
+layout: function
+title: copy
+owner: sean-parent
+brief: Returns a copy of the argument
+tags:
+  - function
+defined_in_file: utility.hpp
+overloads:
+  "template <typename T>\nT copy(const T &)":
+    arguments:
+      - description: __OPTIONAL__
+        name: a
+        type: const T &
+    description: __OPTIONAL__
+    return: __OPTIONAL__
+    signature_with_names: "template <typename T>\nT copy(const T & a)"
+namespace:
+  - stlab
+  - v1
+---
+
+Useful for functions that only take an rvalue reference or that have an explicit copy constructor.
+
+Example:
+```cpp
+void f(vector<int>&&);
+//...
+vector<int> a = ...;
+f(copy(a)); // pass a copy
+f(move(a)); // sink a
+```

docs/tools/docker-tools/README.md

@@ -7,7 +7,7 @@ If you don't already have docker installed, [install Docker](https://docs.docker
 
 ### Building the docker image
 
-To build the docker image, first update the VERSION variable below (please use semantic versioning). Add a [release note](#release-notes).
+To build the docker image, first, update the VERSION variable below (please use semantic versioning). Add a [release note](#release-notes).
 
 ```
 VERSION="1.0.1"
@@ -23,7 +23,7 @@ echo $RUBY_VERSION > ./docs/.ruby-version
 # build the base image, no-cache is used so the latest tools are installed
 docker build --build-arg RUBY_VERSION=$RUBY_VERSION --file ./docs/tools/docker-tools/Dockerfile \
   --target base --tag $VOLUME . \
-  --no-cache 
+  --no-cache
 
 # update the docs environment
 docker run --mount type=bind,source="$(pwd)",target=/mnt/host --tty --interactive $VOLUME bash
@@ -67,14 +67,14 @@ cd /mnt/host
 
 ## Run a local server for the site
 
-Once the site has been prepared, you can run it to see how it looks. From the docker promt enter:
+Once the site has been prepared, you can run it to see how it looks. From the docker prompt enter:
 
 ```
 cd /mnt/host
 ./docs/tools/docs/start.sh
 ```
 
-To view the site, open a browser to `http://localhost:3000`. The site will auto rebuild and refresh as files are changed.
+To view the site, open a browser to `http://localhost:3000`. The site will auto-rebuild and refresh as files are changed.
 
 ## Tips
 
@@ -85,7 +85,7 @@ docker ps
 docker exec -it <container id> bash
 ```
 
-To test a local copy of the jekyll theme, edit the Gemfile and use:
+To test a local copy of the Jekyll theme, edit the Gemfile and use:
 
 ```
 docker run --mount type=bind,source="$(pwd)",target=/mnt/host \
@@ -96,5 +96,5 @@ docker run --mount type=bind,source="$(pwd)",target=/mnt/host \
 
 ### Release Notes
 
-- 1.0.0 - Initial release for jekyll
-- 1.0.1 - Updating tool set
+- 1.0.0 - Initial release for Jekyll
+- 1.0.1 - Updating toolset

stlab/concurrency/await.hpp

@@ -9,19 +9,24 @@
 #ifndef STLAB_CONCURRENCY_AWAIT_HPP
 #define STLAB_CONCURRENCY_AWAIT_HPP
 
+#include <stlab/config.hpp>
+
 #include <chrono>
 #include <condition_variable>
 #include <exception>
 #include <mutex>
 #include <type_traits>
 #include <utility>
 
-#include <stlab/concurrency/default_executor.hpp>
 #include <stlab/concurrency/future.hpp>
 #include <stlab/concurrency/immediate_executor.hpp>
 #include <stlab/concurrency/ready_future.hpp>
 #include <stlab/memory.hpp>
 
+#if STLAB_TASK_SYSTEM(PORTABLE)
+#include <stlab/concurrency/default_executor.hpp>
+#endif
+
 /**************************************************************************************************/
 
 namespace stlab {
@@ -93,8 +98,8 @@ T await(future<T> x) {
     std::condition_variable condition;
     bool flag{false};
 
-    auto hold = std::move(x).recover(immediate_executor, [&](auto&& r) {
-        x = std::forward<decltype(r)>(r);
+    auto hold = std::move(x).recover(immediate_executor, [&](future<T>&& r) {
+        x = std::move(r);
         {
             std::unique_lock<std::mutex> lock{m};
             flag = true;
@@ -201,8 +206,9 @@ template <class T>
 }
 
 template <class T>
-[[deprecated("Use await_for instead.")]] auto blocking_get(
-    future<T> x, const std::chrono::nanoseconds& timeout) -> decltype(x.get_try()) {
+[[deprecated("Use await_for instead.")]] auto blocking_get(future<T> x,
+                                                           const std::chrono::nanoseconds& timeout)
+    -> decltype(x.get_try()) {
     return blocking_get_for(std::move(x), timeout).get_try();
 }