Nuprl Lemma : member_filter2
∀[T:Type]. ∀L:T List. ∀P:ℕ||L|| ⟶ 𝔹. ∀x:T.  ((x ∈ filter2(P;L)) 
⇐⇒ ∃i:ℕ||L||. ((x = L[i] ∈ T) ∧ (↑(P i))))
Proof
Definitions occuring in Statement : 
filter2: filter2(P;L)
, 
l_member: (x ∈ l)
, 
select: L[n]
, 
length: ||as||
, 
list: T List
, 
int_seg: {i..j-}
, 
assert: ↑b
, 
bool: 𝔹
, 
uall: ∀[x:A]. B[x]
, 
all: ∀x:A. B[x]
, 
exists: ∃x:A. B[x]
, 
iff: P 
⇐⇒ Q
, 
and: P ∧ Q
, 
apply: f a
, 
function: x:A ⟶ B[x]
, 
natural_number: $n
, 
universe: Type
, 
equal: s = t ∈ T
Definitions unfolded in proof : 
uall: ∀[x:A]. B[x]
, 
all: ∀x:A. B[x]
, 
member: t ∈ T
, 
so_lambda: λ2x.t[x]
, 
prop: ℙ
, 
and: P ∧ Q
, 
int_seg: {i..j-}
, 
uimplies: b supposing a
, 
guard: {T}
, 
lelt: i ≤ j < k
, 
decidable: Dec(P)
, 
or: P ∨ Q
, 
not: ¬A
, 
implies: P 
⇒ Q
, 
satisfiable_int_formula: satisfiable_int_formula(fmla)
, 
exists: ∃x:A. B[x]
, 
false: False
, 
top: Top
, 
less_than: a < b
, 
squash: ↓T
, 
so_apply: x[s]
, 
select: L[n]
, 
nil: []
, 
it: ⋅
, 
so_lambda: λ2x y.t[x; y]
, 
so_apply: x[s1;s2]
, 
iff: P 
⇐⇒ Q
, 
rev_implies: P 
⇐ Q
, 
l_member: (x ∈ l)
, 
cand: A c∧ B
, 
nat: ℕ
, 
ge: i ≥ j 
, 
le: A ≤ B
, 
less_than': less_than'(a;b)
, 
nat_plus: ℕ+
, 
true: True
, 
uiff: uiff(P;Q)
, 
bool: 𝔹
, 
unit: Unit
, 
btrue: tt
, 
ifthenelse: if b then t else f fi 
, 
bfalse: ff
, 
subtype_rel: A ⊆r B
, 
sq_type: SQType(T)
, 
subtract: n - m
, 
cons: [a / b]
Lemmas referenced : 
list_induction, 
all_wf, 
int_seg_wf, 
length_wf, 
bool_wf, 
iff_wf, 
l_member_wf, 
filter2_wf, 
exists_wf, 
equal_wf, 
select_wf, 
int_seg_properties, 
decidable__le, 
full-omega-unsat, 
intformand_wf, 
intformnot_wf, 
intformle_wf, 
itermConstant_wf, 
itermVar_wf, 
istype-int, 
int_formula_prop_and_lemma, 
istype-void, 
int_formula_prop_not_lemma, 
int_formula_prop_le_lemma, 
int_term_value_constant_lemma, 
int_term_value_var_lemma, 
int_formula_prop_wf, 
decidable__lt, 
intformless_wf, 
int_formula_prop_less_lemma, 
assert_wf, 
istype-universe, 
length_of_nil_lemma, 
filter2_nil_lemma, 
stuck-spread, 
istype-base, 
length_of_cons_lemma, 
list_wf, 
nat_properties, 
nat_wf, 
less_than_wf, 
istype-false, 
add_nat_plus, 
length_wf_nat, 
nat_plus_properties, 
add-is-int-iff, 
itermAdd_wf, 
intformeq_wf, 
int_term_value_add_lemma, 
int_formula_prop_eq_lemma, 
false_wf, 
le_wf, 
equal-wf-T-base, 
bnot_wf, 
not_wf, 
eqtt_to_assert, 
uiff_transitivity, 
eqff_to_assert, 
assert_of_bnot, 
squash_wf, 
true_wf, 
cons_filter2, 
subtype_rel_self, 
iff_weakening_equal, 
cons_wf, 
non_neg_length, 
decidable__equal_int, 
subtype_base_sq, 
int_subtype_base, 
add-member-int_seg2, 
subtract_wf, 
itermSubtract_wf, 
int_term_value_subtract_lemma, 
select_cons_tl, 
select-cons-tl, 
add-subtract-cancel, 
select-cons-hd, 
subtract-add-cancel
Rules used in proof : 
sqequalSubstitution, 
sqequalTransitivity, 
computationStep, 
sqequalReflexivity, 
isect_memberFormation_alt, 
lambdaFormation_alt, 
cut, 
thin, 
introduction, 
extract_by_obid, 
sqequalHypSubstitution, 
isectElimination, 
hypothesisEquality, 
sqequalRule, 
lambdaEquality_alt, 
functionEquality, 
natural_numberEquality, 
hypothesis, 
because_Cache, 
productEquality, 
setElimination, 
rename, 
independent_isectElimination, 
productElimination, 
dependent_functionElimination, 
unionElimination, 
approximateComputation, 
independent_functionElimination, 
dependent_pairFormation_alt, 
int_eqEquality, 
isect_memberEquality_alt, 
voidElimination, 
independent_pairFormation, 
universeIsType, 
imageElimination, 
applyEquality, 
functionIsType, 
baseClosed, 
inhabitedIsType, 
productIsType, 
equalityIsType1, 
universeEquality, 
dependent_set_memberEquality_alt, 
imageMemberEquality, 
equalityTransitivity, 
equalitySymmetry, 
applyLambdaEquality, 
pointwiseFunctionality, 
promote_hyp, 
baseApply, 
closedConclusion, 
addEquality, 
equalityElimination, 
instantiate, 
cumulativity, 
intEquality
Latex:
\mforall{}[T:Type]
    \mforall{}L:T  List.  \mforall{}P:\mBbbN{}||L||  {}\mrightarrow{}  \mBbbB{}.  \mforall{}x:T.    ((x  \mmember{}  filter2(P;L))  \mLeftarrow{}{}\mRightarrow{}  \mexists{}i:\mBbbN{}||L||.  ((x  =  L[i])  \mwedge{}  (\muparrow{}(P  i))))
Date html generated:
2019_10_15-AM-10_55_05
Last ObjectModification:
2018_10_09-AM-10_21_29
Theory : list!
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