There is, in particular, one rule left to template interfaces which are quite interesting: T.47: Avoid highly visible unconstrained templates with common names. Admittedly, the rule T47 is often the reason for unexpected behavior because the wrong function is called.

The topic for today is quite important when you create your type: Regular and SemiRegular types.

This post is about template interfaces due to the C++ core guidelines: "...a critical concept", because a template interface is "a contract between a user and an implementer - and should be carefully designed.".

An interface is a contract between a user and an implementer and should, therefore, be written with great care. This also holds true if you pass an operation as an argument.

Let me continue with the rules for defining concepts in the guidelines. The first of the three remaining rules in this post is quite sophisticated.

Although rule T.11 states: Whenever possible, use standard concepts you sometimes have to define your concepts. This post gives you rules to do it.

We will get concepts with high probability in C++20. Here are the rules from the C++ core guidelines to use them.

Concepts revolutionize the way we think about and use generic programming. They didn't make it in C++11 or C++17 but with C++20, we will get them with a high probability.

In the last post C++ Core Guidelines: Type Erasure, I presented two ways to implement type erasure: void pointers and object orientation. In this post, I bridge dynamic polymorphism (object orientation) with static polymorphism (templates) to get type erasure with templates.

The rule "T.5: Combine generic and OO techniques to amplify their strengths, not their costs"  of the core guidelines to generic programming uses type erasure as an example. Type erasure? Really! Of course, it takes me two posts to explain this advanced template technique.