Applicative: The Forgotten C++ Functional Pattern
Talkat CppCon 2023 · on Wednesday, 2023-10-04· at 14:00· Adams, 6700 North Gaylord Rockies Boulevard·
summary
Shows a concrete implementation: variadic fmap/apply for std::optional and std::expected, a lazy-call wrapper to avoid eager eval, and a Cartesian-product applicative for ranges and tuples that replaces many overloads with one variadic template. Microbenchmarks show the optimizer collapses the wrappers so performance matches handwritten code. Uses parsing examples (quote and hex parsers) and maps p2300 senders/receivers to applicative primitives; the prototypes compile and behave as intended.
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chapters (11)
- 0:00Functional patterns in C++
- 1:55Applicative overlooked
- 9:12Haskell vs C++ applicative
- 17:42Error propagation with applicative
- 27:14Implementing std::expected applicative
- 36:28Applicative vs monad
- 39:25Applicative in C++ ranges
- 46:23List comprehensions
- 51:03Applicative in parsing
- 56:21Applicative with P2300
- 59:33Conclusion & Q&A
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