Functional Composable Operations with Unix-Style Pipes in C++
Let's write C++ code like this shaking off all the verbosity and with 100% domain code and ~0% syntax! Do we really need to explicitly state whether a function is a continuation or a transform?
return get_env("KafkaConsumerConfigFile")
| get_file_contents
| make_client
| connect
| subscribe;
Unix commands seamlessly compose, piping into each other to form a clear train of operations in one line! Similarly in C++, we moved away from non-composable, multi-step processing of ranges using <algorithm>. We embraced the composable <ranges> using pipes. This reduced time & space complexity, improved performance, provided clarity & reduced cognitive load when working with ranges.
But, when NOT dealing with std::ranges, can one work with such easy composability? Why not pipe operations to work with application/business entities! YES, of course, I say! Let's pipe application logic operations & get declarative! HOW HARD COULD IT BE!
With just C++11, we achieve piping operations for any generic T & a Callable. We address Error handling, Resource management, Customizations and Variations like chaining functions taking more than 1 argument or invoking a member function operation instead of free function. Supporting C++20, we make sure our pipe implementation does NOT interfere with std::ranges operations.
Finally, we address the proposed C++23 Monadic interface functions (and_then, transform, or_else) of std::optional and present how we can implement the same without having to explicitly state the verbose and_then, transform, or_else to work with optional. We encounter a surprise on the way & correct overload resolution by employing a concept.
We also discuss critique & compromises of this approach.
Ankur Satle
Ankur is an avid (natural) language learner, but C++ is his mother tongue!
His mantra is: "Effective, Efficient & Elegant". He leverages the power of the small to build large-scale systems. As Smart Data Platform Architect at EXFO, he builds High-performance, Scalable, Telecom Products for 4G/5G Core. He loves working in constrained environments.
He was the Organizer & Host of CppIndiaCon, since inception. His dream came true when he hosted the AMA with Bjarne Stroustrup!
He is the Core Organizer at CppIndia, India's C++ User Group, the most active C++ user group.
He has presented at CppCon 2020 & CppCon 2021, CppIndiaCon 2021 & CppIndiaCon 2022