Improving Our Safety With a Modern C++ Quantities and Units Library
summary
Shows a concrete library: mp‑units implements P2981 to enforce compile‑time physical quantity and unit safety with C++20 (optional C++23) features, no runtime/size overhead, and readable compiler diagnostics. Demonstrates preventing real bugs (Mars Climate Orbiter pounds vs kilograms, Air Canada fuel misunits, Vasa ship rulers) and models quantity kinds, quantity points, vectors/tensors, and safe conversions; reproduces Columbus’s unit miscommunication (≈31% then refined to ≈24% error). Library builds on GCC/Clang today, fails to compile on current MSVC, and is under consideration for C++29 standardization.
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chapters (8)
- 0:00Safety with quantities and units
- 13:55Unit-related disasters
- 20:02MP-units library for C++
- 33:33Unit-safe abstractions
- 46:57Columbus navigation errors
- 59:47Quantity kinds and type safety
- 1:18:08Library pitfalls and limits
- 1:29:59Summary and future
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