refactor(cpp): adopt deducing-this pattern - #295
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…educing this MPGraph carried three const/non-const overload pairs whose bodies were identical (active_begin_iterator, active_end_iterator, get_layer), and MPGraphView carried a fourth copy of get_layer_traversal. An explicit object parameter deduces the const-ness instead of declaring it, which also retires the LayerIterator/ ConstLayerIterator alias pair, and a LayerWindow mixin gives both the graph and its views one get_layer_traversal derived from whatever get_layer they expose -- deducing this rather than CRTP, so neither class names itself as a template argument. MonomialPropagator::mp_op()/indexing() duplicated their require_single_partition_ guard across the two overloads, so the guard string could drift. indexing() reaches its result through a unique_ptr, whose operator* yields a mutable referent whatever the owner's const-ness, so it needs std::forward_like to stay const-correct; new static_asserts pin that down, since nothing else observed it. Assisted-by: ClaudeCode:claude-opus-5
Bitset::data() and PartitionGroup::partition() were const/non-const overload pairs with one body each; partition() dereferences a unique_ptr, so it needs std::forward_like to keep the group's const-ness. The bitwise operators keep their hidden-friend form on purpose. Taking the object parameter by value would make it the working copy and shorten each to one line, but a by-value object parameter is a stack array: NRVO no longer applies, and under -fstack-protector-strong (the platform default) GCC 15 grows operator^ from four instructions to twelve, adding a frame and a canary check to the library's hottest primitive. Recorded in a comment there and as a rule in AGENTS.md, so the next reader does not re-derive it. Assisted-by: ClaudeCode:claude-opus-5
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Summary
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This pull request introduces a significant refactor to the C++ codebase, adopting C++23 "deducing this" member functions to unify const and non-const accessors, reduce code duplication, and improve maintainability. The changes affect several core classes, including
MPGraph,MonomialPropagator,Bitset, and related test files, and also introduce a newLayerWindowmixin to share accessor logic. Additionally, the documentation and test assertions are updated to reflect and verify the new idioms.Adoption of C++23 "deducing this" idiom and accessor refactoring:
Refactored multiple accessor pairs (const/non-const) in
MPGraph,MonomialPropagator,Bitset, andPartitionGroupto single deducing-this member functions, ensuring the returned type's const-ness matches the object and reducing code duplication. This includes methods likeget_layer,mp_op,indexing,partition, anddata[1]](https://github.com/yourrepo/commit/F3345933#diff-L41R40), [2]](https://github.com/yourrepo/commit/F61b741e#diff-L116R116), [3]](https://github.com/yourrepo/commit/F61b741e#diff-L157R156), [4]](https://github.com/yourrepo/commit/F0c67259#diff-L177R181), [5]](https://github.com/yourrepo/commit/Fc93b6da#diff-L106R107)).Introduced the
LayerWindowmixin struct to encapsulate shared layer accessor logic, allowing bothMPGraphandMPGraphViewto inherit and use deducing-this accessors for layer traversal ([cpp/monoprop/detail/graph/MPGraphViews.hR71-R83](https://github.com/yourrepo/commit/Ffaa68d4#diff-L68R68)).Documentation and style guide updates:
AGENTS.mdto recommend deducing-this members for accessor pairs and clarified best practices regarding object parameter passing and NRVO (Named Return Value Optimization) ([AGENTS.mdL173-R183](https://github.com/yourrepo/commit/Fc21d54b#diff-L170R170)).Bitsetand other classes to clarify the rationale behind deducing-this usage and parameter passing choices ([cpp/monoprop/Bitset.hR112-R115](https://github.com/yourrepo/commit/F0c67259#diff-L109R109)).Test and assertion improvements:
General codebase improvements:
<utility>,std::forward_like) to support the new idioms ([cpp/monoprop/detail/partition/PartitionGroup.hR29](https://github.com/yourrepo/commit/Fc93b6da#diff-L26R26)).These changes modernize the codebase, reduce maintenance burden, and ensure safer and clearer accessor patterns throughout the project.
Checklist
docs/,CONTRIBUTING.md) if neededCHANGELOG/ release notes updated if applicableAI/LLM disclosure
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