The C++ Type System Is Your Friend

on YouTube ↗01h 10m

" summary

Argues C++ types and templates enforce domain rules with zero runtime cost: concrete examples include whole value pattern year/month/day wrappers, user‑defined literals, a units/quantity system that does compile‑time dimensional arithmetic (prevents mixes like meters vs feet and the Mars Climate Orbiter failure), and policy‑based fixed_string to handle truncation. Uses CRTP and CRTP base templates plus constexpr checks to move validation to compile time; clang -O3 emits identical assembly, GCC shows only minor differences. Concepts improve error messages.

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" chapters (24)

1. 0:00Intro
2. 0:55Safe, performant, reusable code
3. 3:06(Mostly) typeless programming
4. 6:20Machine-typed programming
5. 8:47Type-rich programming
6. 10:26The miracle of compilation Runtime
7. 13:48Physical types
8. 16:14Whole Value pattern
9. 18:43Templates to the rescue
10. 19:56Adding checking of values
11. 25:46Reuse through client libraries
12. 33:24Physical quantities and dimensions
13. 35:31Tailoring operations - library code
14. 37:12Tailoring operations - client code
15. 39:47Templates and policies
16. 42:38Implementing policies • Let's use a policy on overflow
17. 44:18Constructor validation logic • Let's use a policy to enforce that quantities are non-negative
18. 45:49Effect of constructor validation logic . So, what about the generated code?
19. 46:49Starting to define a domain type . We have now restricted both the operations and the range of allowed values
20. 47:32Domain types vs primitives • Business rules still exist when using primitives: they are just distributed
21. 54:28Compile-time range calculation
22. 55:21Scaling and errors • As systems get larger the number of possible combinations of types (and therefore incompatibilities) grows even faster
23. 56:39Templates and "concepts lite"
24. 59:15Concepts code - first attempt

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