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Diffstat (limited to 'src/development/c++.md')
| -rw-r--r-- | src/development/c++.md | 26 |
1 files changed, 26 insertions, 0 deletions
diff --git a/src/development/c++.md b/src/development/c++.md index 6cdc251..655a603 100644 --- a/src/development/c++.md +++ b/src/development/c++.md @@ -1,5 +1,7 @@ # c++ +Source files of most examples is available [here][src-examples]. + ## Type deduction Force compile error to see what `auto` is deduced to. @@ -16,6 +18,27 @@ typename decltype(foo)::_; {{#include c++/meta.cc:3:}} ``` +## Forwarding reference ([fwd ref][fwd-ref]) + +A `forwarding reference` is a special references that preserves the `value +category` of a function parameter and therefore allows for `perfect` +forwarding. + +A forwarding reference is a parameter of a function template, which is declared +as `rvalue` reference to a `non-cv` qualified `type` template parameter. +```cpp +template<typename T> +void fn(T&& param); // param is a forwarding reference +``` + +Perfect forwarding can be achieved with [`std::forward`][std-fwd]. This for +example allows a wrapper function to pass a parameter with the **exact** same +value category to a down-stream function which is being invoked in the wrapper. + +```cpp +{{#include c++/fwd.cc:3:}} +``` + ## Example: `any_of` template meta function ```cpp @@ -74,3 +97,6 @@ A more detailed description is available in the SO discussion [How does [parameter-pack]: https://en.cppreference.com/w/cpp/language/parameter_pack [enable-if]: https://en.cppreference.com/w/cpp/types/enable_if [sfinae]: https://en.cppreference.com/w/cpp/language/sfinae +[fwd-ref]: https://en.cppreference.com/w/cpp/language/reference#Forwarding_references +[std-fwd]: https://en.cppreference.com/w/cpp/utility/forward +[src-examples]: https://github.com/johannst/notes/tree/master/src/development/c%2B%2B |