HAPI (Open Chain Derivation)

A C++ metaprogramming framework enabling zero-overhead compile-time composition for embedded/IoT systems. Separates container traversal from operation logic under a single evaluation model, letting developers declaratively compose protocol parsers, menu systems, and peripheral abstractions that compile to code equivalent to hand-written, target-specific implementations -- eliminating the per-chip-variant fragmentation (forked code or runtime overhead) endemic to embedded firmware across MCU families like AVR, STM32, ESP32, and RP2040. Demonstrated in production-scale applications and benchmarked favorably against Boost.Hana. Flagship proof-points include OneParse (a JSON parser generated from a ~90-line declarative grammar, competitive with simdjson) and OneMenu (ArduinoMenu's next-generation architecture). Subject of a submission to IEEE Embedded Systems Letters on the underlying Open Chain Derivation pattern. Funding supports core R&D, compile-time diagnostics improvements, and multi-target hardware validation across the broader InternetOfPins library ecosystem (OneParse, OneMenu, OneChip, OneData, OneItem, OneOutput, OnePin, OneBit, OneBus).