Theorem oi0

Description: Definition of the ordinal isomorphism when its arguments are not meaningful. (Contributed by Mario Carneiro, 25-Jun-2015)

	Ref	Expression
Hypothesis	oicl.1	⊢ 𝐹 = OrdIso ( 𝑅 , 𝐴 )
Assertion	oi0	⊢ ( ¬ ( 𝑅 We 𝐴 ∧ 𝑅 Se 𝐴 ) → 𝐹 = ∅ )

Proof

Step	Hyp	Ref	Expression
1		oicl.1	⊢ 𝐹 = OrdIso ( 𝑅 , 𝐴 )
2		df-oi	⊢ OrdIso ( 𝑅 , 𝐴 ) = if ( ( 𝑅 We 𝐴 ∧ 𝑅 Se 𝐴 ) , ( recs ( ( ℎ ∈ V ↦ ( ℩ 𝑣 ∈ { 𝑤 ∈ 𝐴 ∣ ∀ 𝑗 ∈ ran ℎ 𝑗 𝑅 𝑤 } ∀ 𝑢 ∈ { 𝑤 ∈ 𝐴 ∣ ∀ 𝑗 ∈ ran ℎ 𝑗 𝑅 𝑤 } ¬ 𝑢 𝑅 𝑣 ) ) ) ↾ { 𝑥 ∈ On ∣ ∃ 𝑡 ∈ 𝐴 ∀ 𝑧 ∈ ( recs ( ( ℎ ∈ V ↦ ( ℩ 𝑣 ∈ { 𝑤 ∈ 𝐴 ∣ ∀ 𝑗 ∈ ran ℎ 𝑗 𝑅 𝑤 } ∀ 𝑢 ∈ { 𝑤 ∈ 𝐴 ∣ ∀ 𝑗 ∈ ran ℎ 𝑗 𝑅 𝑤 } ¬ 𝑢 𝑅 𝑣 ) ) ) “ 𝑥 ) 𝑧 𝑅 𝑡 } ) , ∅ )
3	1 2	eqtri	⊢ 𝐹 = if ( ( 𝑅 We 𝐴 ∧ 𝑅 Se 𝐴 ) , ( recs ( ( ℎ ∈ V ↦ ( ℩ 𝑣 ∈ { 𝑤 ∈ 𝐴 ∣ ∀ 𝑗 ∈ ran ℎ 𝑗 𝑅 𝑤 } ∀ 𝑢 ∈ { 𝑤 ∈ 𝐴 ∣ ∀ 𝑗 ∈ ran ℎ 𝑗 𝑅 𝑤 } ¬ 𝑢 𝑅 𝑣 ) ) ) ↾ { 𝑥 ∈ On ∣ ∃ 𝑡 ∈ 𝐴 ∀ 𝑧 ∈ ( recs ( ( ℎ ∈ V ↦ ( ℩ 𝑣 ∈ { 𝑤 ∈ 𝐴 ∣ ∀ 𝑗 ∈ ran ℎ 𝑗 𝑅 𝑤 } ∀ 𝑢 ∈ { 𝑤 ∈ 𝐴 ∣ ∀ 𝑗 ∈ ran ℎ 𝑗 𝑅 𝑤 } ¬ 𝑢 𝑅 𝑣 ) ) ) “ 𝑥 ) 𝑧 𝑅 𝑡 } ) , ∅ )
4		iffalse	⊢ ( ¬ ( 𝑅 We 𝐴 ∧ 𝑅 Se 𝐴 ) → if ( ( 𝑅 We 𝐴 ∧ 𝑅 Se 𝐴 ) , ( recs ( ( ℎ ∈ V ↦ ( ℩ 𝑣 ∈ { 𝑤 ∈ 𝐴 ∣ ∀ 𝑗 ∈ ran ℎ 𝑗 𝑅 𝑤 } ∀ 𝑢 ∈ { 𝑤 ∈ 𝐴 ∣ ∀ 𝑗 ∈ ran ℎ 𝑗 𝑅 𝑤 } ¬ 𝑢 𝑅 𝑣 ) ) ) ↾ { 𝑥 ∈ On ∣ ∃ 𝑡 ∈ 𝐴 ∀ 𝑧 ∈ ( recs ( ( ℎ ∈ V ↦ ( ℩ 𝑣 ∈ { 𝑤 ∈ 𝐴 ∣ ∀ 𝑗 ∈ ran ℎ 𝑗 𝑅 𝑤 } ∀ 𝑢 ∈ { 𝑤 ∈ 𝐴 ∣ ∀ 𝑗 ∈ ran ℎ 𝑗 𝑅 𝑤 } ¬ 𝑢 𝑅 𝑣 ) ) ) “ 𝑥 ) 𝑧 𝑅 𝑡 } ) , ∅ ) = ∅ )
5	3 4	syl5eq	⊢ ( ¬ ( 𝑅 We 𝐴 ∧ 𝑅 Se 𝐴 ) → 𝐹 = ∅ )