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 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 • Gentle Not 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 ## I

May 18, 2016 Powered by TCPDF (www.tcpdf.org) Contents 2 The Interactive Theorem Prover 1 Type Providers in Idris Tutorials submitted by community members. Note: The documentation for Idris has been the CC0 can be found online at: http://creativecommons.org/publicdomain/zero/1.0/ Type Providers in Idris Type providers in Idris are simple enough, but there are a few caveats to using them that it would foreign functions, because these will often be used with type providers. ### 1.1 The use case First, let's talk about why we might want type providers. There are a number of reasons to use them and there

July 26, 2016 Powered by TCPDF (www.tcpdf.org) Contents 2 The Interactive Theorem Prover 1 Type Providers in Idris Tutorials submitted by community members. Note: The documentation for Idris has been the CC0 can be found online at: http://creativecommons.org/publicdomain/zero/1.0/ Type Providers in Idris Type providers in Idris are simple enough, but there are a few caveats to using them that it would foreign functions, because these will often be used with type providers. ### 1.1 The use case First, let's talk about why we might want type providers. There are a number of reasons to use them and there

July 26, 2016 Powered by TCPDF (www.tcpdf.org) Contents 2 The Interactive Theorem Prover 1 Type Providers in Idris Tutorials submitted by community members. Note: The documentation for Idris has been the CC0 can be found online at: http://creativecommons.org/publicdomain/zero/1.0/ Type Providers in Idris Type providers in Idris are simple enough, but there are a few caveats to using them that it would foreign functions, because these will often be used with type providers. ### 1.1 The use case First, let's talk about why we might want type providers. There are a number of reasons to use them and there

of a certain type. The variable's type is called static type, the location's type is called dynamic type. If the static type is not the same as the dynamic type, it is a super-type or subtype of of the dynamic type. An identifier is a symbol declared as a name for a variable, type, procedure, etc. The region of the program over which a declaration applies is called the scope of the declaration mod nil not notin object of or out proc ptr raise ref return shl shr static template try tuple type using var when while xor yield Some keywords are unused; they are reserved for future developments

manipulated like any other value. The standard example is the type of lists of a given length $ ^{1} $ , Vect n a, where a is the element type and n is the length of the list and can be an arbitrary term contain values, and where those values describe properties, for example the length of a list, the type of a function can begin to describe its own properties. Take for example the concatenation of two list's length is the sum of the lengths of the two input lists. We can therefore give the following type to the app function, which concatenates vectors: app : Vect n a -> Vect m a -> Vect (n + m)

Tokens 19 1.3 Syntax grammar 23 1.4 Documentation comments 42 2 Type system 43 Glossary 43 Introduction 44 2.1 Type kinds 45 2.1.1 Built-in types 46 kotlin.Any 46 kotlin.Nothing 46 types 48 2.1.3 Type parameters ..... 50 Function type parameters ..... 51 Mixed-site variance ..... 51 Declaration-site variance ..... 52 Use-site variance ..... 54 2.1.4 Type capturing .... . 55 2.1.5 Type containment ..... 60 2.1.6 Function types ..... 61 Suspending function types ..... 62 2.1.7 Flexible types ..... 63 Dynamic type ..... 64 Platform types ..... 64 2.1.8 Nullable

Literals 70 8.13 Annotated Strings 70 9 Functions 72 9.1 Argument Passing Behavior 73 9.2 Argument-type declarations 74 9.3 The return Keyword 75 9.4 Operators Are Functions 77 9.5 Operators With Special Types 127 12.1 Type Declarations 128 12.2 Abstract Types 130 12.3 Primitive Types 132 12.4 Composite Types 133 12.5 Mutable Composite Types 135 CONTENTS 12.6 Declared Types 136 12.7 Type Unions 137 12 9 UnionAll Types 146 12.10 Singleton types 147 12.11 Types of functions 148 12.12 Type{T} type selectors 149 12.13 Type Aliases 150 12.14 Operations on Types 151 12.15 Custom pretty-printing 152 12.16 “Value

8.13 Annotated Strings 70 9 Functions 72 9.1 Argument Passing Behavior 73 9.2 Argument-type declarations 74 9.3 The return Keyword 75 9.4 Operators Are Functions 77 9.5 Operators With 127 12.1 Type Declarations 128 12.2 Abstract Types 130 12.3 Primitive Types 132 12.4 Composite Types 133 12.5 Mutable Composite Types 135 12.6 Declared Types ..... 136 12.7 Type Unions ... 12.10 Singleton types ..... 147 12.11 Types of functions ..... 148 12.12 Type{T} type selectors ..... 149 12.13 Type Aliases ..... 150 12.14 Operations on Types ..... 151 12.15 Custom pretty-printing

8.13 Annotated Strings 70 9 Functions 72 9.1 Argument Passing Behavior 73 9.2 Argument-type declarations 74 9.3 The return Keyword 75 9.4 Operators Are Functions 77 9.5 Operators With 127 12.1 Type Declarations 128 12.2 Abstract Types 130 12.3 Primitive Types 132 12.4 Composite Types 133 12.5 Mutable Composite Types 135 12.6 Declared Types ..... 136 12.7 Type Unions ... 12.10 Singleton types ..... 147 12.11 Types of functions ..... 148 12.12 Type{T} type selectors ..... 149 12.13 Type Aliases ..... 150 12.14 Operations on Types ..... 151 12.15 Custom pretty-printing