@hackage/circuits

Total revamp of the API around a single normal-form GADT and a clearer separation between syntax and semantics.

New core vocabulary

Circuit.Loop.Loop t arr a b is the free traced monoidal category in normal form: either Lift (a base arrow) or Knot (a feedback loop). Composition fuses via the Category instance, so every value has at most one Knot at the top.
Circuit.Free.Free is the free category (Lift, Compose).
Circuit.Sym.Sym is the free symmetric monoidal category (Lift, Compose, Par, Swap).
Circuit.Net.Net is the free traced PROP with a bimonoid: Lift, Compose, Par, Swap, Knot, Copy, Discard, Plus, Zero. Wiring stays inspectable for transpose, metering, and fusion.
Circuit.Hyper.Hyper is the final coinductive encoding; encode and observe move between Loop and Hyper.

Semantics split across two tracks

Structural semantics: Circuit.Category.Category → Circuit.Channel.Channel → Circuit.Channel.Strength → Circuit.Channel.Traced.
Functorial semantics: Circuit.Category.Category → Circuit.Tensor.Tensor → Circuit.Tensor.Action.

Layer tower

Circuit.Layer.Layer unifies the free-forgetful folds: unit, run, bind, lower. Law, Run, and Bind associated types capture what each layer needs from its target and source categories.

Ends, boxes, and queues

Circuit.Ends replaces the old Circuit.Box and Circuit.Queue modules. Companion/conjoint ends (Out, In), matched Ends, box, boxAsymmetric, Queue strategies, openSTM, and openIO all live here.

Dagger and bimonoid

Circuit.Dagger consolidates CopyDiscard, MergeZero, Bimonoid, Dagger, and transpose.

À-la-carte syntax

Circuit.Algebra provides compositional signatures (SigCompose, SigKnot, SigPar, SigSwap, SigBimonoid) and direct GADT ↔︎ syntax isomorphisms (algLoop, runAlgLoop, algNet, runAlgNet).

Operators

Forward composition is (.>); backward composition is (.) from Control.Category.
Forward/backward application operators (|>) and (<|) live in Circuit.Category.

Removed

Circuit.Trace / Circuit GADT name retired to Circuit.Loop.
Circuit.Strength, Circuit.Monoidal, Circuit.Classes, Circuit.Adjunction, Circuit.Signature, Circuit.Box, Circuit.Queue, Circuit.Loopd, and Circuit.Dup are gone; their contents are merged or renamed as above.
cellIO, openCollectSTM, openCollectIO, openBatchSTM, openBatchMaybeSTM, freeToMon, monTranspose, AlgSymKnot, loopToSymKnot, and the old traceToAlg / algToTrace names are removed. Helpers that are not core API moved to circuits-examples.
The signature-tests Cabal test suite is removed; verification is via cabal-docspec and cabal check.

Examples and companion libraries

@hackage / circuits