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Metamath Proof Explorer

Theorem funoprabg

Description: "At most one" is a sufficient condition for an operation class abstraction to be a function. (Contributed by NM, 28-Aug-2007)

Ref Expression
Assertion funoprabg ( ∀ 𝑥 ∀ 𝑦 ∃* 𝑧 𝜑 → Fun { ⟨ ⟨ 𝑥 , 𝑦 ⟩ , 𝑧 ⟩ ∣ 𝜑 } )

Proof

Step Hyp Ref Expression
1 mosubopt ⊢ ( ∀ 𝑥 ∀ 𝑦 ∃* 𝑧 𝜑 → ∃* 𝑧 ∃ 𝑥 ∃ 𝑦 ( 𝑤 = ⟨ 𝑥 , 𝑦 ⟩ ∧ 𝜑 ) )
2 1 alrimiv ⊢ ( ∀ 𝑥 ∀ 𝑦 ∃* 𝑧 𝜑 → ∀ 𝑤 ∃* 𝑧 ∃ 𝑥 ∃ 𝑦 ( 𝑤 = ⟨ 𝑥 , 𝑦 ⟩ ∧ 𝜑 ) )
3 dfoprab2 ⊢ { ⟨ ⟨ 𝑥 , 𝑦 ⟩ , 𝑧 ⟩ ∣ 𝜑 } = { ⟨ 𝑤 , 𝑧 ⟩ ∣ ∃ 𝑥 ∃ 𝑦 ( 𝑤 = ⟨ 𝑥 , 𝑦 ⟩ ∧ 𝜑 ) }
4 3 funeqi ⊢ ( Fun { ⟨ ⟨ 𝑥 , 𝑦 ⟩ , 𝑧 ⟩ ∣ 𝜑 } ↔ Fun { ⟨ 𝑤 , 𝑧 ⟩ ∣ ∃ 𝑥 ∃ 𝑦 ( 𝑤 = ⟨ 𝑥 , 𝑦 ⟩ ∧ 𝜑 ) } )
5 funopab ⊢ ( Fun { ⟨ 𝑤 , 𝑧 ⟩ ∣ ∃ 𝑥 ∃ 𝑦 ( 𝑤 = ⟨ 𝑥 , 𝑦 ⟩ ∧ 𝜑 ) } ↔ ∀ 𝑤 ∃* 𝑧 ∃ 𝑥 ∃ 𝑦 ( 𝑤 = ⟨ 𝑥 , 𝑦 ⟩ ∧ 𝜑 ) )
6 4 5 bitr2i ⊢ ( ∀ 𝑤 ∃* 𝑧 ∃ 𝑥 ∃ 𝑦 ( 𝑤 = ⟨ 𝑥 , 𝑦 ⟩ ∧ 𝜑 ) ↔ Fun { ⟨ ⟨ 𝑥 , 𝑦 ⟩ , 𝑧 ⟩ ∣ 𝜑 } )
7 2 6 sylib ⊢ ( ∀ 𝑥 ∀ 𝑦 ∃* 𝑧 𝜑 → Fun { ⟨ ⟨ 𝑥 , 𝑦 ⟩ , 𝑧 ⟩ ∣ 𝜑 } )