BT0091

factorial_zero

Stable ยท empty-context checked

The relational factorial of zero is one.

Exact expanded PA statement

forall n z. n = 0 -> (exists ff_b_zero ff_c_zero. ((forall ff_i_zero_range. (exists ff_lt_zero_range_bound. ff_lt_zero_range_bound + S ff_i_zero_range = n) -> (((exists ff_h_zero_range_decoded. ff_h_zero_range_decoded + S (1 + ff_i_zero_range) = S ((S (ff_i_zero_range)) * ff_c_zero)) /\ exists ff_q_zero_range_decoded. ff_b_zero = ff_q_zero_range_decoded * S ((S (ff_i_zero_range)) * ff_c_zero) + (1 + ff_i_zero_range)))) /\ (exists ff_u_zero_product ff_v_zero_product. ((((exists ff_h_zero_product_start. ff_h_zero_product_start + S (1) = S ((S (0)) * ff_v_zero_product)) /\ exists ff_q_zero_product_start. ff_u_zero_product = ff_q_zero_product_start * S ((S (0)) * ff_v_zero_product) + (1))) /\ ((((exists ff_h_zero_product_terminal. ff_h_zero_product_terminal + S (z) = S ((S (n)) * ff_v_zero_product)) /\ exists ff_q_zero_product_terminal. ff_u_zero_product = ff_q_zero_product_terminal * S ((S (n)) * ff_v_zero_product) + (z))) /\ forall ff_i_zero_product. (exists ff_lt_zero_product_bound. ff_lt_zero_product_bound + S ff_i_zero_product = n) -> exists ff_p_zero_product ff_r_zero_product ff_s_zero_product. ((((exists ff_h_zero_product_factor. ff_h_zero_product_factor + S (ff_p_zero_product) = S ((S (ff_i_zero_product)) * ff_c_zero)) /\ exists ff_q_zero_product_factor. ff_b_zero = ff_q_zero_product_factor * S ((S (ff_i_zero_product)) * ff_c_zero) + (ff_p_zero_product))) /\ ((((exists ff_h_zero_product_partial. ff_h_zero_product_partial + S (ff_r_zero_product) = S ((S (ff_i_zero_product)) * ff_v_zero_product)) /\ exists ff_q_zero_product_partial. ff_u_zero_product = ff_q_zero_product_partial * S ((S (ff_i_zero_product)) * ff_v_zero_product) + (ff_r_zero_product))) /\ ((((exists ff_h_zero_product_successor. ff_h_zero_product_successor + S (ff_s_zero_product) = S ((S (S ff_i_zero_product)) * ff_v_zero_product)) /\ exists ff_q_zero_product_successor. ff_u_zero_product = ff_q_zero_product_successor * S ((S (S ff_i_zero_product)) * ff_v_zero_product) + (ff_s_zero_product))) /\ ff_s_zero_product = ff_r_zero_product * ff_p_zero_product)))))))) -> z = 1

Structural proof guide

The relational factorial of zero is one.

Direct prerequisites: beta_product_zero. The authored body proceeds by case analysis (3), equality transport (4).

Proof neighborhood

Direct dependencies

Direct dependents

Formal native tactic body

Dependencies are hypotheses of this body receipt. The focused endpoint audits separately check the complete empty-context certificates.

  1. 0001intro n
  2. 0002intro z
  3. 0003intro hn
  4. 0004intro hfactorial
  5. 0005rewrite hn at hfactorial
  6. 0006rewrite hn at hfactorial
  7. 0007rewrite hn at hfactorial
  8. 0008rewrite hn at hfactorial
  9. 0009cases hfactorial
  10. 0010cases hfactorial_witness
  11. 0011cases hfactorial_witness_witness
  12. 0012specialize beta_product_zero x
  13. 0013specialize beta_product_zero x1
  14. 0014specialize beta_product_zero z
  15. 0015apply beta_product_zero
  16. 0016exact hfactorial_witness_witness_right