SL000G · theorem body

doubling_floor_below_implies_double_at_most_half

Alpha v34 checked-use · independently kernel and Lean verified; not Stable

A source at most the odd-half floor has doubled value at most the half.

Current library: Alpha v34, 4,223 checked-use theorems; Stable remains 432. Historical first admissions, original proof editions, and non-admitted aliases are preserved. Exact original first-admission records.

Statement with defined notation

∀ h. ∀ k. ∀ x. h = 2 · k ∨ h = 2 · k + 1 → Le(x,k)Le(2 · x,h)

Every purple notation token opens its conservative definition. This reading surface never changes the unchanged intuitionistic kernel or confers checked-use authority.

Definitions used by this theorem

In the theorem statement

In local proof propositions

Exact expanded first-order statement
forall h k x. (((h = 2 * k) \/ (h = 2 * k + 1))) -> (exists qst_le_floor. qst_le_floor + (x) = (k)) -> (exists qst_le_doubled. qst_le_doubled + (2 * x) = (h))

Proof neighborhood

Direct theorem prerequisites

mul_le_mul_left · Stable closed add_succ_left · Stable closed

Direct theorem dependents

Definition-aware tactic body

Only propositions whose conservative expansion has been checked for exact first-order equivalence are compacted. Every changed line retains its immutable exact replay command.

Read the argument

Proof checkpoints

21 script commands · 10 reading checkpoints · 1 local claims

This is a reading aid, not a new proof or a proof-tree certificate. Checkpoint groups are consecutive commands, not inferred branch boundaries. Every step links to the preserved script.

Definition notation is shown below. Open the paired exact edition for the original native formulas. Source pairing is not a new equivalence certificate.

01Fix variables and assumptionsL1–5

Work with arbitrary variables or the premises of the current implication.

  1. L1
    intro h
  2. L2
    intro k
  3. L3
    intro x
  4. L4
    intro hhalf
  5. L5
    intro hfloor
02Establish hscaledL6–11

Establish this local claim before using it. It is not an additional assumption. The following proof commands apply mul le mul left.

  1. L6
    have hscaled : Le(2 · x,2 · k)Definitions: Le(2 · x,2 · k)Original native command in the exact edition
  2. L7
    specialize mul_le_mul_left x
  3. L8
    specialize mul_le_mul_left k
  4. L9
    specialize mul_le_mul_left 2
  5. L10
    apply mul_le_mul_left
  6. L11
    exact hfloor
03Separate the logical casesL12–12

Follow the explicit conjunction, disjunction, witness, or contradiction step recorded below.

  1. L12
    cases hhalf
04Calculate and transport equalitiesL13–13

Carry out the recorded arithmetic or equality steps; inspect the exact commands for their direction and premises.

  1. L13
    rewrite hhalf_left
05Use earlier factsL14–14

Instantiate or apply named facts and discharge the corresponding proof obligations.

  1. L14
    exact hscaled
06Separate the logical casesL15–15

Follow the explicit conjunction, disjunction, witness, or contradiction step recorded below.

  1. L15
    cases hscaled
07Construct an explicit witnessL16–16

Supply the displayed value, then prove that it has the required property.

  1. L16
    exists S x1
08Calculate and transport equalitiesL17–17

Carry out the recorded arithmetic or equality steps; inspect the exact commands for their direction and premises.

  1. L17
    trans S (x1 + 2 * x)
09Use earlier factsL18–18

Instantiate or apply named facts and discharge the corresponding proof obligations.

  1. L18
    apply add_succ_left
10Calculate and transport equalitiesL19–21

Carry out the recorded arithmetic or equality steps; inspect the exact commands for their direction and premises.

  1. L19
    rewrite hscaled_witness
  2. L20
    rewrite hhalf_right
  3. L21
    simp

Library-wide reading audit

Original defined command ledger · 21 lines
  1. 0001intro h
  2. 0002intro k
  3. 0003intro x
  4. 0004intro hhalf
  5. 0005intro hfloor
  6. 0006have hscaled : Le(2 · x,2 · k)
    Exact native replay linehave hscaled : exists gap. gap + 2 * x = 2 * k
  7. 0007specialize mul_le_mul_left x
  8. 0008specialize mul_le_mul_left k
  9. 0009specialize mul_le_mul_left 2
  10. 0010apply mul_le_mul_left
  11. 0011exact hfloor
  12. 0012cases hhalf
  13. 0013rewrite hhalf_left
  14. 0014exact hscaled
  15. 0015cases hscaled
  16. 0016exists S x1
  17. 0017trans S (x1 + 2 * x)
  18. 0018apply add_succ_left
  19. 0019rewrite hscaled_witness
  20. 0020rewrite hhalf_right
  21. 0021simp