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Project-declaredLean 4.31.0 · mathlib@fabf563a7c95

Dist From Code le iff rel Dist From Code le

Code.distFromCode_le_iff_relDistFromCode_le

Plain-language statement

A word u is close to a code C within an absolute error bound e if and only if it is close within the equivalent relative error bound e / n.

Exact Lean statement

theorem distFromCode_le_iff_relDistFromCode_le {C : Set (ι → F)} [Nonempty ι] (u : ι → F) (e : ℕ) :
    Δ₀(u, C) ≤ e ↔ δᵣ(u, C) ≤ (e : ℝ≥0) / (Fintype.card ι : ℝ≥0)

Formal artifact

Lean source

Canonical source
Full Lean sourceLean 4
theorem distFromCode_le_iff_relDistFromCode_le {C : Set F)} [Nonempty ι] (u : ι  F) (e : ) :    Δ₀(u, C)  e  δᵣ(u, C)  (e : 0) / (Fintype.card ι : 0) := by  have h_n_pos : 0 < Fintype.card ι := Fintype.card_pos  have h_n_pos_nnreal : 0 < (Fintype.card ι : 0) := by exact_mod_cast h_n_pos  rw [closeToCode_iff_closeToCodeword_of_minDist]  conv_rhs => rw [ENNReal.coe_div (hr := by    simp only [ne_eq, Nat.cast_eq_zero, Fintype.card_ne_zero, not_false_eq_true])]  rw [relCloseToCode_iff_relCloseToCodeword_of_minDist (u := u) (C := C):= (e : 0) / (Fintype.card ι : 0))]  apply exists_congr  intro v  simp only [and_congr_right_iff]  intro hv_mem  rw [pairRelDist_le_iff_pairDist_le]  simp only [isUnit_iff_ne_zero, ne_eq, Nat.cast_eq_zero, Fintype.card_ne_zero, not_false_eq_true,    IsUnit.div_mul_cancel, Nat.floor_natCast]
Project
ArkLib
License
Apache-2.0
Commit
fad5cbf80877
Source
ArkLib/Data/CodingTheory/Basic/RelativeDistance.lean:328-343

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Affine gaps lifted to interleaved codes

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Project documentation

This lemma proves the final algebraic step in the DG25 Theorem 3.1 proof. It shows that if R > e + 1, then e * (R / (R - 1)) < e + 1. The intuition is that the fraction R / (R - 1) is always greater than 1, but as R gets larger, it gets closer to 1. The hypothesis R > e + 1 provides a strong enough bound to ensure the product e * (fraction) do...

cryptographyproof systemscoding theory

Source project: ArkLib

Person-level attribution pending.

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Project-declaredLean 4.31.0

Gadget Decompose coeff

ArkLib.Lattices.Ajtai.gadgetDecompose_coeff

Plain-language statement

The k-th coefficient (k < deg φ) of a gadget-decomposition block is exactly the corresponding digit of the corresponding input coefficient.

cryptographyproof systemscoding theory

Source project: ArkLib

Person-level attribution pending.

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Project-declaredLean 4.31.0

Gadget Decompose lawful

ArkLib.Lattices.Ajtai.gadgetDecompose_lawful

Plain-language statement

The base-b gadget decomposition is a lawful gadget decomposition.

cryptographyproof systemscoding theory

Source project: ArkLib

Person-level attribution pending.

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