OCaml 5.5.0 has been released with several significant language and runtime improvements. Key highlights include module-dependent functions (modular explicits) enabling lightweight functors as function arguments, a relocatable compiler that can be moved without breaking bytecode runtime compatibility, higher-rank polymorphic function arguments via explicit type annotations, and an expanded String standard library with search/replace/split functions using the 2-way string matching algorithm. The release also introduces generalized local definitions, external types for better FFI integration with GADTs, and GC improvements including a new sweep-only phase and idle phase. Additionally, around 60 new standard library functions, ~90 improvements, ~40 bug fixes, and Windows concurrency primitives now use WinAPI instead of Winpthreads.
