## CppCon 2020 Template Metaprogramming: Type Traits Part 1 Jody Hagins jhagins@maystreet.com coachhagins@gmail.com ## CppCon 2020 Template Metaprogramming: Type Traits Introduction ## I ntended Audience depth, slow current - Not necessarily beginner to C++, but beginner to traditional template metaprogramming techniques ## I ntended Audience • Beginner/Intermediate • Gentle entry: swimming pool to river depth, slow current - Not necessarily beginner to C++, but beginner to traditional template metaprogramming techniques • Type traits part of standard library for ~10 years ## I ntended Audience • Beginner/Intermediate

## Template-Less MetaProgramming 0 ## +24 ## KRIS JUSIAK 2024 September 15 - 20 ## Template Metaprogramming (TMP) template using meta_fun = this_talk; ## te::Metaprogramming::is_hard); // ✓ ?static_assert(Template::Metaprogramming::is_hard); // ✓ ?static_assert(Template::Metaprogramming::is_powerful); // ✓ ?static_assert(Template::Metaprogramming::is_hard); static_assert(Template::Metaprogramming::is_powerful); // ✓ ?static_assert(( Template::Metaprogramming::is_easy and Template::Metaprogramming::is_powerful and Template::Metaprogramming::has_nice_error_messages

4.3 Induction and Calculation 42 4.4 Axioms 45 5 Using Automation in Lean 46 6 Metaprogramming in Lean 47 Bibliography # Overview This introduction offers a tour of Lean and its features results are indeed correct. Which brings us to yet another aspect of Lean, namely, its role as a metaprogramming language. Many of Lean’s internal data structures and procedures are exposed and available within language of Lean itself, via a monadic interface. We refer to the use of these procedures as “metaprogramming” because they take us outside the formal framework: the access points to the API are declared

Global Variables ..... 214 Multiple Objects ..... 215 Macro-generated code ..... 215 27 Metaprogramming ..... 217 27.1 Program representation ..... 217 Symbols ..... 218 27.2 Expressions and evaluation Powerful shell-like capabilities for managing other processes • Lisp-like macros and other metaprogramming facilities Part II Julia v1.3 Release Notes Powered by TCPDF (www.tcpdf.org) ## Chapter 2 ## described below, are some examples of non-standard string literals. Other examples are given in the Metaprogramming section. ### 16.9 Regular Expressions Julia has Perl-compatible regular expressions (regexes)

member_info.name() << std::endl; ## How is this different from metaprogramming? ## Reflection vs metaprogramming ## • Not much:) • Operate on values instead of types ☐ Syntactic difference find function signature? ■ P3096 helps :) "Function Parameter Reflection" Can also do metaprogramming (Boost.CallableTraits etc) ## • Runtime virtual interface means cannot use template types ☀️ signature? ■ P3096 helps :) "Function Parameter Reflection in Reflection" Can also do metaprogramming (Boost.CallableTraits etc) • Runtime virtual interface means cannot use template types • Type

expected. Some C++ computations run at compile-time by using constexpr, consteval, or template metaprogramming. These compile-time components can also be tested at compile-time. ## Unit Tests Setup The using T2 = decltype(*itr); static_assert(is_same_v ## Compiler Loophole – Stateful Metaprogramming • A friend function exists outside of the class it is declared in. - When a template class record operations • Uses macros to record control flow • Uses compiler loophole for stateful metaprogramming ## C++26 Reflection Use std::meta::info to record generic actions. Query std::meta::info to

uments/9/a/3/c/9a3c029d0db11594467a24cca15ee3f1/p4_1.jpg) Language Evolution API Design Metaprogramming Tricks ## About the talk • Expressiveness in C++ • Parsers • Operator overloading • Domain “…The syntax and techniques needed are pretty horrendous.” - C++ core guidelines (template metaprogramming) struct plus_exp : foldl_reject_incomplete_start_with_parser

elegance template Programming with a value-based language  ## Programming with a value-based Language  criticize initialization in C++ • There are so many ways... • …

evaluation of user-defined functions, and cross-module inlining, in combination with the preference for value-based, stack-located data types, lead to extremely efficient code. Multi-threading, asynchronous input/output runtime, and JIT-Compilers (Just-In-Time) are a very special variant of metaprogramming. Nim allows the use of macros and metaprogramming only at compile-time, so unpredictable and possibly dangerous code modifications But as Nim's macros and metaprogramming capacities are very powerful, they can make it more difficult to understand and reason about the source code. So metaprogramming should be used with some care

evaluation of user-defined functions, and cross-module inlining, in combination with the preference for value-based, stack-located data types, lead to extremely efficient code. Multi-threading, asynchronous input/output runtime, and JIT-Compilers (Just-In-Time) are a very special variant of metaprogramming. Nim allows the use of macros and metaprogramming only at compile-time, so unpredictable and possibly dangerous code modifications But as Nim's macros and metaprogramming capacities are very powerful, they can make it more difficult to understand and reason about the source code. So metaprogramming should be used with some care