Template Metaprogramming: Type Traits Part 1 CppCon 2020 1 Jody Hagins
 jhagins@maystreet.com 
 coachhagins@gmail.comTemplate Metaprogramming: Type Traits CppCon 2020 2 IntroductionIntended Audience oriented: shallow depth, slow current • Not necessarily beginner to C++, but beginner to traditional template metaprogramming techniques 3Intended Audience • Beginner/Intermediate • Gentle entry: swimming oriented: shallow depth, slow current • Not necessarily beginner to C++, but beginner to traditional template metaprogramming techniques • Type traits part of standard library for ~10 years 3Intended Audience

1 / 58Template Metaprogramming (TMP) Template Metaprogramming (TMP) template using meta_fun = this_talk; 2 / 58❓static_assert(Template::Metaprogramming::is_hard); // ✔ 3 / 58❓s 58❓static_assert(Template::Metaprogramming::is_hard); // ✔ ❓static_assert(Template::Metaprogramming::is_powerful); // ✔ 3 / 58❓static_assert(Template::Metaprogramming::is_hard); // ✔ ❓static_assert( ❓static_assert(Template::Metaprogramming::is_powerful); // ✔ ❓static_assert(( Template::Metaprogramming::is_easy and Template::Metaprogramming::is_powerful and Template::Metaprogramming::has_nice_error_messages

first view Writing more views Write views that actually do something Raising a 404 error Use the template system Removing hardcoded URLs in templates Namespacing URL names Writing your first Django app Django Form classes Working with form templates Further topics Templates Support for template engines The Django template language Class-based views Introduction to class-based views Built-in class-based Installation Usage Django’s cache framework Setting up the cache The per-site cache The per-view cache Template fragment caching The low-level cache API Downstream caches Using Vary headers Controlling cache:

. . . . . . . . . . . . 1 1.3 The model layer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 1.4 The view layer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 1.5 The template layer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 1.6 Forms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 529 4.5 Custom template tags and filters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 534

Overview Writing more views Write views that actually do something Raising a 404 error Use the template system Removing hardcoded URLs in templates Namespacing URL names Writing your first Django app Django Form classes Working with form templates Further topics Templates Support for template engines The Django template language Class-based views Introduction to class-based views Built-in class-based Installation Usage Django’s cache framework Setting up the cache The per-site cache The per-view cache Template fragment caching The low-level cache API Downstream caches Using Vary headers Controlling cache:

. . . . . . . . . . . . 2 1.4 The model layer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 1.5 The view layer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 1.6 The template layer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 1.7 Forms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 555 4.5 Custom template tags and filters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 559

Overview Writing more views Write views that actually do something Raising a 404 error Use the template system Removing hardcoded URLs in templates Namespacing URL names Writing your first Django app Django Form classes Working with form templates Further topics Templates Support for template engines The Django template language Class-based views Introduction to class-based views Built-in class-based Installation Usage Django’s cache framework Setting up the cache The per-site cache The per-view cache Template fragment caching The low-level cache API Downstream caches Using Vary headers Controlling cache:

. . . . . . . . . . . . 2 1.4 The model layer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 1.5 The view layer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 1.6 The template layer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 1.7 Forms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 561 4.5 Custom template tags and filters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 566

Overview Writing more views Write views that actually do something Raising a 404 error Use the template system Removing hardcoded URLs in templates Namespacing URL names Writing your first Django app Django Form classes Working with form templates Further topics Templates Support for template engines The Django template language Class-based views Introduction to class-based views Built-in class-based Installation Usage Django’s cache framework Setting up the cache The per-site cache The per-view cache Template fragment caching The low-level cache API Downstream caches Using Vary headers Controlling cache: