feat: Bitstring encodings - #21
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August 1, 2026 14:19
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Hopefully with these changes it should also be possible to refactor existing files like:
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August 1, 2026 22:57
# Conflicts: # Complexitylib/Models/RoseTreeMachine/Data.lean
`dev` de-exposed `Encoding/DataEncode.lean` as part of the module-interface minimization, but this branch adds `bitstringEncode` together with `bitstringEncode_def` and `bitstringEncode_injective`, both of which need the definition's body to typecheck. Expose the single definition rather than re-exposing the whole module. Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
`dev` gained commit 60118c9 ("revert encoding stuff") via the SamuelSchlesinger#23 merge, which deleted Complexitylib/Encoding.lean and Encoding/Delimit.lean and inlined the delimiting logic back into Encoding/Pairing.lean. That is the exact refactor this branch performs, so the merge conflicts on both files. Resolved in favour of this branch's extraction: keep Encoding.lean and Encoding/Delimit.lean, and restore this branch's Encoding/Pairing.lean (`pair x y = delimit x ++ y`). No declaration is lost — every declaration in dev's Pairing.lean is present in this branch's Pairing.lean plus Delimit.lean. Also restore the `Complexitylib.Encoding` import in Complexitylib.lean, which the merge dropped because dev deleted the line. The two `pair`s produce the same bitstring but associate differently (`(A ++ sep) ++ y` here vs `A ++ (sep ++ y)` on dev), so five consumer proofs needed the shape realigned: - SAT/ThreeSAT/Verifier: unfold `delimit` in the `foldl_append` chain - TuringMachine/Subroutines/PairEmit/Internal: add `delimit` to `simpa` - TuringMachine/UTM/Internal/Init: add `delimit` to `simp` - Classes/NP/Internal/PairBuildTM: drop now-unused `List.append_assoc` - Classes/PPoly/Advice: drop now-unused `List.append_assoc` Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
…layer `Data` and the `DataEncode` typeclass are machine-independent: `Data` is the rose tree the RTM operates on, but it is also the target every `DataEncode` instance encodes into, so it does not belong under `Models/RoseTreeMachine/`. Move `Models/RoseTreeMachine/Data.lean` to `Encoding/Data.lean` and `Models/RoseTreeMachine/DataEncode.lean` to `Encoding/DataEncode.lean`, and repoint the three import statements that referred to the old paths. Nothing else changes. `Encoding/Data.lean` is byte-identical to the file it replaces; `Encoding/DataEncode.lean` differs only in its own import of `Data`. Namespaces, module docs, comments and declarations are all untouched, so the `Complexity.RoseTreeMachine` namespace is preserved for now. Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
…ncoding # Conflicts: # Complexitylib/Encoding/Data.lean # Complexitylib/Models.lean
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This PR adds bitstring encodings, trying to make it a bit more natural to express e.g. polytime computability on arbitrary input types.
As a part of this it refactors the "delimiting" operation out of the current definition of
pair, to reuse for other typeclass derivations.What this adds on top of #25
Encoding/Delimit.lean— the self-delimiting block framing extracted out ofpair,plus its parsers (
unpair?,undelimitBlock,takeFirstBlock,hasBlock,tagBlock,undelimitBlocks) and their correctness lemmasEncoding/Pairing.lean—pair x ybecomesdelimit x ++ yEncoding/Data.lean—Data.toBits/Data.fromBits, the round-tripData.fromBits_toBits, injectivityData.toBits_injective, andData.size_lt_of_memEncoding/DataEncode.lean—DataEncode.bitstringEncodeand its injectivity,plus the
List BoolinstanceThe two
pairdefinitions produce the same bitstring but associate differently, so fiveconsumer proofs are realigned (
ThreeSAT/Verifier,PairEmit/Internal,UTM/Internal/Init,PairBuildTM,PPoly/Advice). No statement is weakened.Open question
There is a
DataEncodeclass which encodes into arbitrary-arity trees; it may be better tojust encode those trees as lists. Worth settling before this leaves draft, since it changes
this same API surface.
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