Meeting C++ 2025 - From Acrobatics to Ergonomics - A Field Report on How to Make Libraries Helpful

Joel FALCOU

On Day 2 at 16:00 (CET/Berlin) in Track B [Opal Room and online]

Thanks to features like concepts, C++20 promised to make template meta-programming more approachable and expressive, especially for library designers. But as we quickly learned, template programming can still be surprising or frustrating — in the worst-case scenario, it's both.

In this talk, I’ll share lessons from the past 3–4 years of building high-performance, user-friendly C++ libraries, including: 

• EVE, a SIMD abstraction layer designed for performance and portability.
• KUMI, a re-imagined tuple library with algorithmic support.
• KIWAKU, a toolkit for multi-dimensional arrays that aims to be efficient and ergonomic.

We’ll explore the practical challenges of designing ergonomic C++ APIs:

• Error messages that make sense: `static_assert` or concepts? How to avoid large template error stacks? ... 
• APIs that align with user intuition: How do we provide options on the functions' semantics? How to design meaningful extension points, ...
• How bold design decisions can pay off: going sideways with standard practices, turning CTAD upside-down, ...

We'll discuss how C++20 features helped us reduce friction and increase clarity once we use them properly.
If you’ve ever screamed into the void over template errors, please join in!

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