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 necessarily beginner to C++, but beginner to traditional template metaprogramming techniques • Type traits part of standard library for ~10 years 3Intended Audience • Beginner/Intermediate • Gentle necessarily beginner to C++, but beginner to traditional template metaprogramming techniques • Type traits part of standard library for ~10 years • Fundamentals have been in use for ~20 years 3Intended

We == WG21 + community There is no C/C++ language. Write contemporary C++ An opportunityComplete type-and-resource safety • Is an ideal (aim) of C++ • From very early on (1979) • But “being careful” model for achieving that can be found in A brief introduction to C++'s model for type- and resource-safety (2015) and Type-and-resource safety in modern C++ (2021). • No limitations of what can be expressed Except necessary range checking Stroustrup - C++ safety -CppCon - October 2023 7Type-and-resource safety • Every object is accessed according to the type with which it was defined (type safety) • Every object

Argument Passing Behavior . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73 9.2 Argument-type declarations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 74 9.3 The return Keyword . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 125 12 Types 127 12.1 Type Declarations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 128 12.2 Abstract Declared Types . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 136 12.7 Type Unions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 137 12.8 Parametric

Argument Passing Behavior . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73 9.2 Argument-type declarations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 74 9.3 The return Keyword . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 125 12 Types 127 12.1 Type Declarations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 128 12.2 Abstract Declared Types . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 136 12.7 Type Unions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 137 12.8 Parametric

Argument Passing Behavior . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73 9.2 Argument-type declarations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 74 9.3 The return Keyword . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 125 12 Types 127 12.1 Type Declarations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 128 12.2 Abstract Declared Types . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 136 12.7 Type Unions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 137 12.8 Parametric

Argument Passing Behavior . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 68 8.2 Argument-type declarations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69 8.3 The return Keyword . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 119 11 Types 120 11.1 Type Declarations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 121 11.2 Abstract Declared Types . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 129 11.7 Type Unions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 129 11.8 Parametric

Argument Passing Behavior . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 68 8.2 Argument-type declarations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69 8.3 The return Keyword . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 119 11 Types 120 11.1 Type Declarations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 121 11.2 Abstract Declared Types . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 129 11.7 Type Unions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 129 11.8 Parametric

one for each different platform and configuration: operating system, architecture, compiler, build type, etc. These binaries can be created and uploaded to a server with the same commands in all platforms ConanCenter. You can search there for libraries and also check the available versions. In our case, after checking the available versions for Zlib we choose to use one of the latest versions: zlib/1.2.11. The easiest apple-clang 14.0 apple-clang>=13, using the major as version Detected profile: [settings] arch=x86_64 build_type=Release compiler=apple-clang compiler.cppstd=gnu17 compiler.libcxx=libc++ compiler.version=14 os=Macos

one for each different platform and configuration: operating system, architecture, compiler, build type, etc. These binaries can be created and uploaded to a server with the same commands in all platforms ConanCenter. You can search there for libraries and also check the available versions. In our case, after checking the available versions for Zlib we choose to use one of the latest versions: zlib/1.2.11. The easiest apple-clang 14.0 apple-clang>=13, using the major as version Detected profile: [settings] arch=x86_64 build_type=Release compiler=apple-clang compiler.cppstd=gnu17 compiler.libcxx=libc++ compiler.version=14 os=Macos

Argument Passing Behavior . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73 9.2 Argument-type declarations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 74 9.3 The return Keyword . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 125 12 Types 127 12.1 Type Declarations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 128 12.2 Abstract Declared Types . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 136 12.7 Type Unions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 137 12.8 Parametric