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

VirtualBox is a so-called “hosted” hypervisor (sometimes referred to as a “type 2” hypervi- sor). Whereas a “bare-metal” or “type 1” hypervisor would run directly on the hardware, VirtualBox requires an “Programs” menu, click on the item in the “VirtualBox” group. On Vista or Windows 7, you can also type “VirtualBox” in the search box of the “Start” menu. • On a Mac OS X host, in the Finder, double-click in either the “System” or “System Tools” group of your “Applications” menu. Alternatively, you can type VirtualBox in a terminal. When you start VirtualBox for the first time, a window like the following

VirtualBox is a so-called “hosted” hypervisor (sometimes referred to as a “type 2” hypervi- sor). Whereas a “bare-metal” or “type 1” hypervisor would run directly on the hardware, VirtualBox requires an “Programs” menu, click on the item in the “VirtualBox” group. On Vista or Windows 7, you can also type “VirtualBox” in the search box of the “Start” menu. • On a Mac OS X host, in the Finder, double-click in either the “System” or “System Tools” group of your “Applications” menu. Alternatively, you can type VirtualBox in a terminal. When you start VirtualBox for the first time, a window like the following

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 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 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 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 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