isInt_of (Correctness of expression code)

Proved

NLogN.IState.isInt_of

by xuanji · Oct 17, 2026 · Mathlib 0df444a (Lean v4.33.1)

complexity-theoryinteger-multiplicationkappa-improvement

The following holds (Lean statement, in the scope of module NLogN.HExprPf):

theorem NLogN.IState.isInt_of {s : IState S} {i : Fin S} {a : ℤ} {L : List Item}
    (h : s.G i = .int a :: L) : s.IsInt i

Context. The lemma belongs to the part Correctness of expression code.

Formalization Note. This lemma belongs to layer 5 of the Lean formalization (integer-multiplication-kappa campaign) of the OpenAI preprint Integer multiplication below $n\log n$ : the uniform item-language machine (register programs over the NLogN multitape framework) assembling the Proposition 14 / Lemma 13 / Proposition 18 pieces, the resampling and chirp stages and the cost recurrences into one fixed machine, culminating in NLogN.KFTop.kappa_bound : IntMul.KappaBound (1 / 2 ^ 182) (the bound of Def_IntMul_MultitapeModel). All names refer to the definition bundles up to IntMul_Kappa_K_Defs33.

Preamble

-- OpenAI-preprint / κ-improvement development (integer-multiplication-kappa), generated by skeleton subtraction.

import Definitions.Def_IntMul_Kappa_K_Defs33

set_option autoImplicit false
set_option relaxedAutoImplicit false
set_option maxHeartbeats 1000000

open NLogN
open IntMul
variable {S P : ℕ} {I : List Sym} {iprog : Fin P → IStmt S P}

Formal statement

theorem NLogN.IState.isInt_of {s : IState S} {i : Fin S} {a : ℤ} {L : List Item}
    (h : s.G i = .int a :: L) : s.IsInt i := by sorry

Source

OpenAI, Integer multiplication below n log n (preprint, 23 Sep 2026), https://github.com/openai/math/tree/adc7f1241b42e322a6451854ab7e4b4c146bf78a/preprints/Integer-multiplication-below-n-log-n-September-23-2026. Lemma `NLogN.IState.isInt_of` of the Lean development NLogN/HExprPf.lean (lines 21–22), integer-multiplication-kappa campaign.

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