Database
SUPPLEMENTARY MATERIAL (USERS' MATHBOXES)
Mathbox for Zhi Wang
Examples of categories
Parallel-arrow categories
parhomcl
Metamath Proof Explorer
Description: All hom-sets of the parallel-arrow construction lie in its arrow
carrier. (Contributed by Zhi Wang , 14-Sep-2026) (Revised by Zhi
Wang , 16-Sep-2026)
Ref
Expression
Hypotheses
parhomval.h
⊢ H = x ∈ B , y ∈ B ⟼ if x = y J if x = X ∧ y = Y S ∅
parhomssun.k
⊢ K = S ∪ J
parhomcl.f
⊢ φ → F ∈ U H V
Assertion
parhomcl
⊢ φ → F ∈ K
Proof
Step
Hyp
Ref
Expression
1
parhomval.h
⊢ H = x ∈ B , y ∈ B ⟼ if x = y J if x = X ∧ y = Y S ∅
2
parhomssun.k
⊢ K = S ∪ J
3
parhomcl.f
⊢ φ → F ∈ U H V
4
1 2
parhomssun
⊢ U H V ⊆ K
5
4 3
sselid
⊢ φ → F ∈ K