What are they?

• Allows you to:
  • delay binding of type to variables
  • write generic code of some type T
  • trades code size for binary size (and readability?)

Template Methods

• Will deduce but not coerce types
• They can be overloaded

Classes vs Functions

• Functions have type deduction
• Classes/Structs have partial specialization
• At least for now…

Templates with Polymorphism

• If possible,
  • Put only template methods in a template class
  • Each expansion takes space in the binary
  • Each expansion increases compile time

Variadic Templates

• Templates of many arguments
• Use overloading to handle recursion

SFINAE

Substitution Failure is not an Error

• A blessing and a curse
  • Almost incomprehensible error messages
  • Allows overloading and “compile-time reflection”
    • Reflection – change behavior on class attribute/methods

Trait Specialization and Policies

• Select an algorithm/behavior through:
  • reflection on types
  • template arguments
• Implementations vary
  • SFINAE-based – more flexible, harder to implement
  • Specialization-base – less flexible, almost trivial

Template Meta-programming

• Solve a recursive problem at compile time
• often inline, beware template recursion depth

Tuples

• collections of types
• very similar to a struct
• can be expanded and passed as function arguments
• can be used to extract variables via std::tie

Functors

• Accept a function as argument
• Write functional paradigm code
  • Easier to parallelize
  • Easier to reason about

Other Uses

• Smart Pointers
• Iterator Generics
• Curiously Recurring Template Pattern
• Parameterized Type Attributes
• Generic implementations of Design Patterns