Changelog

All notable changes to this project will be documented in this file.

The format is based on Keep a Changelog, and this project adheres to Semantic Versioning.

[Unreleased]

PeriodicArray gained a fifth type parameter G for the inverse map (imap). The type signature changed from PeriodicArray{T,N,A,F} to PeriodicArray{T,N,A,F,G}. Any code with explicit type annotations, dispatch rules, or type introspection on the four-parameter form will need to be updated.
The internal field previously named .map is now named .fmap; a new field .imap holds the inverse map. Direct field access must be updated accordingly.
The module was reorganised into separate source files (types.jl, indexing.jl, broadcast.jl, vector_interface.jl, repeat.jl, circshift.jl, reverse.jl, mapped_ref.jl).

PeriodicArray now accepts an explicit imap argument (the inverse map used by setindex!). When omitted, imap defaults to NegatedShiftMap(fmap), i.e. (x, shifts...) -> fmap(x, -shifts...), preserving the previous behaviour. Supplying a custom imap is useful when fmap is not self-inverse under shift negation, or when mutation should be explicitly forbidden (pass an imap that throws).
New MappedRef type and mapped_ref(arr, I...) function. mapped_ref returns a lazy, mutable wrapper for an out-of-bounds element that applies the forward map on reads and the inverse map on writes, solving the long-standing limitation where iterated indexing for mutation silently did nothing (e.g. x[i][j] = v).