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Project-declaredLean 4.31.0 · mathlib@fabf563a7c95

Dist eq min Wt Codewords

LinearCode.dist_eq_minWtCodewords

Plain-language statement

The min distance of a linear code equals the minimum of the weights of non-zero codewords.

Exact Lean statement

lemma dist_eq_minWtCodewords [Ring F] {A : Type*} [DecidableEq A] [AddCommGroup A] [Module F A]
    {MC : ModuleCode ι F A} :
  Code.minDist (MC : Set (ι → A)) = minWtCodewords MC

Formal artifact

Lean source

Canonical source
Full Lean sourceLean 4
lemma dist_eq_minWtCodewords [Ring F] {A : Type*} [DecidableEq A] [AddCommGroup A] [Module F A]    {MC : ModuleCode ι F A} :  Code.minDist (MC : Set A)) = minWtCodewords MC := by    unfold Code.minDist minWtCodewords    refine congrArg _ (Set.ext fun _  fun u, _, v, _  u - v, ?p₁, fun _  0, ?p₂⟩⟩) <;>    rename_i u hu v u_sub_v_weight hvv h_u_mem hv_u_v_rel    -- aesop (add simp [hammingDist_eq_wt_sub, sub_eq_zero])    constructor    · rcases hv_u_v_rel with h_v_mem, h_u_ne_v, h_dist      apply Submodule.sub_mem      · exact h_u_mem      · exact h_v_mem    · -- case p₂      rcases hv_u_v_rel with h_v_mem, h_u_ne_v, h_dist      constructor      · rw [sub_ne_zero]; exact h_u_ne_v      · -- ⊢ Code.wt (u - v) = hv        -- We know `Code.wt c = h_u_mem`, so we show `Δ₀(0, c) = Code.wt c`        rw [ h_dist]        simp [Code.wt, hammingDist, sub_eq_zero]    · simp only [SetLike.mem_coe, ne_eq, hammingDist_zero_left]      rcases hv_u_v_rel with c, h_c_mem, h_c_ne, h_c_wt      -- We need to prove the conjunction      constructor      · -- 1. Prove `0 ∈ MC`        let res := Submodule.zero_mem (p := MC)        exact res      · -- 2. Prove `∃ v_1 ...`        refine c, h_c_mem, ?_, ?_        · -- Prove `¬0 = c` (which is `0 ≠ c`)          exact h_c_ne.symm        · -- Prove `‖c‖₀ = h_u_mem`          rw [h_c_wt]          simp only [hammingNorm, ne_eq, Code.wt]
Project
ArkLib
License
Apache-2.0
Commit
fad5cbf80877
Source
ArkLib/Data/CodingTheory/Basic/LinearCode.lean:424-457

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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...

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Project-declaredLean 4.31.0

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Plain-language statement

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Source project: ArkLib

Person-level attribution pending.

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Project-declaredLean 4.31.0

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ArkLib.Lattices.Ajtai.gadgetDecompose_lawful

Plain-language statement

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Source project: ArkLib

Person-level attribution pending.

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