Taming Lambdas' uniqueness

on YouTube ↗59m

" summary

C++ lambdas each produce a unique closure type, which breaks passing, storing, or comparing them; concrete fixes are shown: use templates for zero overhead, use std::move_only_function or type erasure when dynamic storage is needed, and prefer indirection or static polymorphism when performance matters. A reusable functors container with an invoke map and cached invokers gets near-template speed and beats std::function; benchmarks report about 3× faster than std::function on GCC and sometimes Clang fully optimizes away indirection.

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" chapters (34)

1. 0:00Lambda uniqueness problem
2. 1:28Core problem with identical lambdas
3. 3:15C++ unique closure types
4. 5:20Non-capturing lambdas to function pointers
5. 7:48Capturing lambdas and function pointers
6. 10:15Scenario with three different lambdas
7. 11:40Passing lambdas via templates
8. 13:04std::function and move-only variants
9. 16:13Benchmarking lambda passing
10. 17:43Storing lambdas in containers
11. 19:10Factory for identical lambdas
12. 20:58Move-only lambdas in containers
13. 22:00Solutions for different signatures
14. 23:03Benchmarking lambda storage
15. 25:11Performance of std::function
16. 26:17Custom type eraser for lambdas
17. 28:51Evaluating custom type eraser
18. 29:34Syntax for lambda container
19. 30:15Static polymorphism with overload
20. 32:45Parameter packs and concepts
21. 33:46Functors container structure
22. 35:09Constructing functors container
23. 36:14Deduction guides for container
24. 37:17Adding elements to container
25. 39:48Handling references in push_back
26. 41:10Calling all container lambdas
27. 43:59Calling lambdas by index
28. 46:05Benchmarking custom container
29. 47:07Dynamic dispatch with runtime index
30. 48:54Implementing invoke map
31. 51:45Performance of invoke map
32. 53:14Optimizing invoke map with caching
33. 55:20Final benchmarks and takeaways
34. 55:41Conclusion and Q&A

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