Nuprl Lemma : ifthenelse_functionality_wrt_rev_implies2
∀b1,b2:𝔹. ∀[p,q1,q2:ℙ]. (b1 = b2 ⇒ {q1 ⇐ q2} ⇒ {if b1 then p else q1 fi ⇐ if b2 then p else q2 fi })
Proof
Definitions occuring in Statement :
ifthenelse: if b then t else f fi ,
bool: 𝔹,
uall: ∀[x:A]. B[x],
prop: ℙ,
guard: {T},
all: ∀x:A. B[x],
rev_implies: P ⇐ Q,
implies: P ⇒ Q,
equal: s = t ∈ T
Definitions unfolded in proof :
guard: {T},
all: ∀x:A. B[x],
uall: ∀[x:A]. B[x],
implies: P ⇒ Q,
rev_implies: P ⇐ Q,
member: t ∈ T,
bool: 𝔹,
unit: Unit,
it: ⋅,
btrue: tt,
uiff: uiff(P;Q),
and: P ∧ Q,
uimplies: b supposing a,
ifthenelse: if b then t else f fi ,
assert: ↑b,
iff: P ⇐⇒ Q,
true: True,
prop: ℙ,
sq_type: SQType(T),
bfalse: ff,
exists: ∃x:A. B[x],
or: P ∨ Q,
bnot: ¬bb,
false: False
Lemmas referenced :
bool_wf,
eqtt_to_assert,
subtype_base_sq,
bool_subtype_base,
iff_imp_equal_bool,
btrue_wf,
assert_wf,
true_wf,
eqff_to_assert,
equal_wf,
bool_cases_sqequal,
assert_of_bnot,
ifthenelse_wf,
rev_implies_wf
Rules used in proof :
sqequalSubstitution,
sqequalRule,
sqequalReflexivity,
sqequalTransitivity,
computationStep,
lambdaFormation,
isect_memberFormation,
cut,
hypothesisEquality,
thin,
introduction,
extract_by_obid,
hypothesis,
sqequalHypSubstitution,
unionElimination,
equalityElimination,
isectElimination,
productElimination,
independent_isectElimination,
instantiate,
cumulativity,
independent_pairFormation,
natural_numberEquality,
because_Cache,
equalitySymmetry,
dependent_functionElimination,
independent_functionElimination,
equalityTransitivity,
dependent_pairFormation,
promote_hyp,
voidElimination,
universeEquality
Latex:
\mforall{}b1,b2:\mBbbB{}.
\mforall{}[p,q1,q2:\mBbbP{}]. (b1 = b2 {}\mRightarrow{} \{q1 \mLeftarrow{}{} q2\} {}\mRightarrow{} \{if b1 then p else q1 fi \mLeftarrow{}{} if b2 then p else q2 fi \})
Date html generated:
2017_04_14-AM-07_30_10
Last ObjectModification:
2017_02_27-PM-02_58_42
Theory : bool_1
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