@hackage/exchangealgebra

union (and therefore (.+) / mappend / fromList) misassociated a value with the wrong base when one operand was a zero-valued singleton. For (v1:@b1) .+ (v2:@b2) with isZeroValue v1, the result was v2:@b1 — the surviving nonzero value relabeled onto the zero posting's base (symmetrically v1:@b2 when v2 was zero). A zero contributes nothing, so the result must be v2:@b2 / v1:@b1 (the nonzero value on its own base). The bug preserved norm (the total was unchanged) but corrupted per-base projection (proj / projWithBase / balanceBy / stock & profit queries): a value silently moved to a neighboring base. It was construction-order sensitive — ledgers that build explicit 0:@base singletons via the raw (:@) constructor (e.g. sparsified input coefficients in agent-based simulations) would, depending on accumulation order, invent a phantom posting on an adjacent base. In the bundled simulation example this shifted a company's reported stock by up to ~30% over 100 terms. One-line fix in Algebra.hs union, covered by the new testUnionZeroSingletonBase unit test. (Independently confirmed root cause.)

nearlyEqScaled — scale-aware approximate equality (|x - y| <= atol + rtol * max |x| |y|, with atol = 1e-13, rtol = 1e-12).

bases ignored the _notSide Seq and iterated _hatSide twice (src/ExchangeAlgebra/Algebra.hs, regression existed since the introduction of the HashMap-backed Liner representation). The previous implementation produced length (bases x) != length (vals x) whenever the Hat-side and Not-side Seqs of any base had different lengths, dropped entries whose Hat-side Seq was empty, and duplicated Hat-side entries with the wrong label. A 1-character fix (hs → ns in the outer fold) restores the intended behaviour, covered by a new testBasesNotSideRegression unit test.

Reconciliation comparators (bar / (.-), balance, diffRL, barNormPair) now use a scale-aware tolerance instead of a fixed 1e-13 absolute tolerance. Behaviour change: near-balanced values at large magnitudes no longer retain floating-point rounding noise as a spurious residual, and balance / diffRL no longer use exact == / > comparisons.
isNearlyNum returns False (instead of raising error) when a NaN makes every ordered comparison fail, so non-finite inputs can no longer crash the check.

Journal.toAlg avoids materializing an intermediate Map.elems base list.
Removed an unused Control.Parallel.Strategies import from ExchangeAlgebra.Algebra.

Documented the spill-to-disk path (runSimulationWithSpill / runScenariosWithSpill with SpillDeletePolicy) as the recommended approach for constant-memory large-scale simulations, in the README and the ExchangeAlgebra.Simulate module header (example: sim2).
Added the original axiomatic source (Deguchi & Nakano, Axiomatic Foundations of Vector Accounting, Systems Research 3(1):31–39, 1986) to the README References section.

First release prepared for Hackage publication.

First Hackage-ready release with full metadata and dependency version bounds.
LSM-style Journal with spill-to-disk support for large simulations.
Significant performance improvements across Algebra, Journal, and the simulation engine.

LSM-style Journal data structure with spill engine and binary spill restore.
Boilerplate-reducing helpers for state-space simulation (UpdatableSTRef, UpdatableSTArray, generalized Updatable instances).
Sparse sigma map APIs (sigmaFromMap, sigma2When, sigmaOnFromMap, etc.) and a map-based fold path for purchases.
filterByAxis for Journal and matching tests.
finalStockTransfer fast path for both Algebra and Journal.
restoreJournalFromBinarySpill and related spill utilities in ExchangeAlgebra.Write.
New examples covering ripple-effect and stock simulations.
Self-contained writeCSV / csvTranspose in ExchangeAlgebra.Write (removes the previous Git-only csv-parser dependency).

Refactored Journal axis indexing for nested-IntMap storage.
Refactored ExchangeAlgebra.Algebra and the simulation pipeline for sparse processing.
Optimized projection paths (proj, projNorm, projWithBaseNorm, projWithNoteNorm).
Optimized Hashable / Binary instances and Element equality.
Optimized the transfer engine and finalStockTransfer path.
Refined sim2 readability and stabilized build warnings.

Bumped Stackage resolver from lts-22.6 (GHC 9.6.3) to lts-24.4 (GHC 9.10.2).
Added explicit version bounds for all library dependencies.
Added synopsis, category, and corrected description URL in package.yaml.
Removed Git-only csv-parser (CSVParserT) dependency, replaced with in-tree writeCSV / csvTranspose in ExchangeAlgebra.Write.
Added CSV write tests (testCsvWriteCSV, testCsvTranspose, etc.).
Removed unused bifunctors dependency (dead import in ExchangeAlgebra.Algebra).

Removed the non-hierarchical top-level module ExchangeAlgebraJournal. Use ExchangeAlgebra.Journal (for the Journal data model) or the top-level ExchangeAlgebra (for the Algebra data model) instead. The ExchangeAlgebra top-level remains an Algebra-layer umbrella; Journal users should import ExchangeAlgebra.Journal as the unqualified umbrella and qualify ExchangeAlgebra.Algebra as needed.

Added extension guidance and import guidance to the Haddock of ExchangeAlgebra.Algebra.Base.Element, clarifying that user code should import Element via the higher-level umbrella modules.

Integrated the high-speed ExchangeAlgebra.Map library into the main ExchangeAlgebra module.
Added basic ripple-effect modules and Leontief inverse computation.
Switched the internal data structure to HashMap for faster lookups.
Added ExchangeAlgebra.Simulate and parallelized ripple effect computation.
Generalized simulation functions and adopted ST s for StateSpace.
Added sigma / sigmaM helpers for summation over indices.

Initial development release of the Exchange Algebra library (algebraic description of bookkeeping based on Hiroshi Deguchi's framework).