Nuprl Lemma : bunion-value-type
∀[A,B:Type].  (value-type(A ⋃ B)) supposing (value-type(B) and value-type(A))
Proof
Definitions occuring in Statement : 
value-type: value-type(T)
, 
b-union: A ⋃ B
, 
uimplies: b supposing a
, 
uall: ∀[x:A]. B[x]
, 
universe: Type
Definitions unfolded in proof : 
uall: ∀[x:A]. B[x]
, 
member: t ∈ T
, 
uimplies: b supposing a
, 
b-union: A ⋃ B
, 
so_lambda: λ2x.t[x]
, 
so_apply: x[s]
, 
all: ∀x:A. B[x]
, 
implies: P 
⇒ Q
, 
bool: 𝔹
, 
unit: Unit
, 
it: ⋅
, 
btrue: tt
, 
uiff: uiff(P;Q)
, 
and: P ∧ Q
, 
ifthenelse: if b then t else f fi 
, 
bfalse: ff
, 
exists: ∃x:A. B[x]
, 
prop: ℙ
, 
or: P ∨ Q
, 
sq_type: SQType(T)
, 
guard: {T}
, 
bnot: ¬bb
, 
assert: ↑b
, 
false: False
, 
value-type: value-type(T)
, 
has-value: (a)↓
Lemmas referenced : 
tunion-value-type, 
bool_wf, 
ifthenelse_wf, 
eqtt_to_assert, 
eqff_to_assert, 
equal_wf, 
bool_cases_sqequal, 
subtype_base_sq, 
bool_subtype_base, 
assert-bnot, 
equal-wf-base, 
b-union_wf, 
base_wf, 
value-type_wf
Rules used in proof : 
sqequalSubstitution, 
sqequalTransitivity, 
computationStep, 
sqequalReflexivity, 
isect_memberFormation, 
introduction, 
cut, 
sqequalRule, 
extract_by_obid, 
sqequalHypSubstitution, 
isectElimination, 
thin, 
hypothesis, 
lambdaEquality, 
instantiate, 
hypothesisEquality, 
universeEquality, 
cumulativity, 
independent_isectElimination, 
lambdaFormation, 
unionElimination, 
equalityElimination, 
because_Cache, 
productElimination, 
dependent_pairFormation, 
promote_hyp, 
dependent_functionElimination, 
equalityTransitivity, 
equalitySymmetry, 
independent_functionElimination, 
voidElimination, 
isect_memberEquality, 
axiomSqleEquality
Latex:
\mforall{}[A,B:Type].    (value-type(A  \mcup{}  B))  supposing  (value-type(B)  and  value-type(A))
Date html generated:
2017_04_14-AM-07_36_40
Last ObjectModification:
2017_02_27-PM-03_08_58
Theory : subtype_1
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