STLhajotus

STLhajotus is a conceptual extension to the C++ Standard Template Library focused on partitioning and distributing data within STL containers. It provides a set of utilities and views that enable decomposing a single container into multiple subranges or buckets, which can then be processed independently or in parallel while maintaining a unified interface with existing STL algorithms and the ranges framework.

Key ideas include split views that expose subranges, bucketing or distribution by predicate or hash, and composition with existing algorithms. It emphasizes lazy evaluation and non-owning views to avoid unnecessary copying. It supports both stateless splits based on position or index and stateful splits based on element characteristics.

Typical usage involves creating a partitioner that targets a container, distributing elements into a fixed number of buckets or according to a predicate, and then performing parallel transformations or reductions on each subrange. The results can be merged back into a single container or used to drive concurrent tasks with the standard library's execution policies.

Implementation considerations include compatibility with std::ranges, memory efficiency, and predictable iteration semantics. STLhajotus aims to be header-only and zero-copy where possible, with a design that plays well with existing iterators, iterating over subranges without copying elements.

Origin and status: STLhajotus is described in this article as a hypothetical extension to the STL, used to illustrate partitioning patterns in modern C++ development. It is not part of the official C++ standard; several libraries experiment with similar ideas for range-based partitioning and parallel processing.