Templates

On my previous post about C++ Policies, a policy-based design was used for comparators and loggers, which are stateless function objects (they only call a single function). These types are empty, but as members they still occupy space because C++ guarantees distinct addresses for distinct subobjects. With C++20’s [[no_unique_address]] or Empty Base Optimization (EBO), programmers can make these truly zero-cost, which is huge for small, hot objects like iterators or adapters.1 ...

I’ve been reading about templates a lot lately and kept seeing the word policy. Which made me realized I wanted a single post that answers the question: What is a policy? Why do C++ sources keep mentioning them? How do compile-time policies (templates) compare to runtime strategies (virtuals/std::function)? And when should which be used? ...

Introduction C++20 shipped with Concepts — a long‑awaited way to express constraints on template parameters right where they live. Concepts turn the old “SFINAE and traits soup” into clear, readable predicates that the compiler can check for you. If you’ve ever stared at a 20‑line enable_if just to say “this needs to be integral,” this feature is for you. ...