CD0008

finite_add_lt_of_le_of_lt

Alpha v34 independently verified · alpha_closed; checked-use authorized; not Stable

A weak left inequality and strict right inequality give a strict sum inequality.

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.

Exact expanded first-order arithmetic statement

forall a b c d. (exists fms_gap_le. fms_gap_le + (a) = (b)) -> (exists fms_gap_lt. fms_gap_lt + S (c) = (d)) -> (exists fms_gap_lt. fms_gap_lt + S (a+c) = (b+d))

Constructive proof overview

Generated structural guide

A weak left inequality and strict right inequality give a strict sum inequality.

The unchanged tactic script uses 1 declared prerequisite and contains 18 exact native proof lines.

Alpha v34 checked-use · first admitted v27 · independently kernel and Lean verified; not Stable

Proof neighborhood

Direct dependencies

CD0006 finite_add_le_add

Direct dependents

CD000B finite_sum_pointwise_strict_at

Formal native tactic body

Dependencies are introduced as named hypotheses before line 1. Local theorem links identify exact declared prerequisites. This exact body belongs to a complete independently kernel-checked constructive proof bundle and has Alpha checked-use authority; it does not imply Stable membership.

Read the argument

Proof checkpoints

18 script commands · 3 reading checkpoints · 2 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.

Named ingredients (1)
finite add le add
01Fix variables and assumptionsL1–6

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

  1. L1
    intro a
  2. L2
    intro b
  3. L3
    intro c
  4. L4
    intro d
  5. L5
    intro hab
  6. L6
    intro hcd
02Establish htL7–14

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

  1. L7
    have ht : exists fms_gap_le. fms_gap_le + (a+(S c)) = (b+d)
  2. L8
    specialize finite_add_le_add a
  3. L9
    specialize finite_add_le_add b
  4. L10
    specialize finite_add_le_add S c
  5. L11
    specialize finite_add_le_add d
  6. L12
    apply finite_add_le_add
  7. L13
    exact hab
  8. L14
    exact hcd
03Establish heL15–18

Establish this local claim before using it. It is not an additional assumption. The following proof commands apply PA4.

  1. L15
    have he : a+(S c)=S(a+c)
  2. L16
    apply PA4
  3. L17
    rewrite he at ht
  4. L18
    exact ht

Library-wide reading audit

Original exact command ledger · 18 lines
  1. 0001intro a
  2. 0002intro b
  3. 0003intro c
  4. 0004intro d
  5. 0005intro hab
  6. 0006intro hcd
  7. 0007have ht : exists fms_gap_le. fms_gap_le + (a+(S c)) = (b+d)
  8. 0008specialize finite_add_le_add a
  9. 0009specialize finite_add_le_add b
  10. 0010specialize finite_add_le_add S c
  11. 0011specialize finite_add_le_add d
  12. 0012apply finite_add_le_add
  13. 0013exact hab
  14. 0014exact hcd
  15. 0015have he : a+(S c)=S(a+c)
  16. 0016apply PA4
  17. 0017rewrite he at ht
  18. 0018exact ht