Nuprl Lemma : int-list-index-property
∀x:ℤ. ∀L:ℤ List.  (((x ∈ L) 
⇐⇒ int-list-index(L;x) < ||L||) ∧ ((x ∈ L) 
⇒ (L[int-list-index(L;x)] = x ∈ ℤ)))
Proof
Definitions occuring in Statement : 
int-list-index: int-list-index(L;x)
, 
l_member: (x ∈ l)
, 
select: L[n]
, 
length: ||as||
, 
list: T List
, 
less_than: a < b
, 
all: ∀x:A. B[x]
, 
iff: P 
⇐⇒ Q
, 
implies: P 
⇒ Q
, 
and: P ∧ Q
, 
int: ℤ
, 
equal: s = t ∈ T
Definitions unfolded in proof : 
all: ∀x:A. B[x]
, 
uall: ∀[x:A]. B[x]
, 
member: t ∈ T
, 
so_lambda: λ2x.t[x]
, 
prop: ℙ
, 
and: P ∧ Q
, 
subtype_rel: A ⊆r B
, 
int_seg: {i..j-}
, 
iff: P 
⇐⇒ Q
, 
rev_implies: P 
⇐ Q
, 
implies: P 
⇒ Q
, 
uimplies: b supposing a
, 
so_apply: x[s]
, 
select: L[n]
, 
nil: []
, 
it: ⋅
, 
so_lambda: λ2x y.t[x; y]
, 
top: Top
, 
so_apply: x[s1;s2]
, 
cand: A c∧ B
, 
not: ¬A
, 
false: False
, 
ge: i ≥ j 
, 
guard: {T}
, 
lelt: i ≤ j < k
, 
satisfiable_int_formula: satisfiable_int_formula(fmla)
, 
exists: ∃x:A. B[x]
, 
int-list-index: int-list-index(L;x)
, 
so_lambda: so_lambda(x,y,z.t[x; y; z])
, 
so_apply: x[s1;s2;s3]
, 
bool: 𝔹
, 
unit: Unit
, 
btrue: tt
, 
uiff: uiff(P;Q)
, 
ifthenelse: if b then t else f fi 
, 
nat_plus: ℕ+
, 
less_than: a < b
, 
squash: ↓T
, 
less_than': less_than'(a;b)
, 
true: True
, 
decidable: Dec(P)
, 
or: P ∨ Q
, 
sq_type: SQType(T)
, 
bfalse: ff
, 
bnot: ¬bb
, 
assert: ↑b
, 
nequal: a ≠ b ∈ T 
, 
cons: [a / b]
, 
le: A ≤ B
Lemmas referenced : 
list_induction, 
iff_wf, 
l_member_wf, 
less_than_wf, 
int-list-index_wf, 
int_seg_wf, 
length_wf, 
equal-wf-base, 
int_subtype_base, 
list_subtype_base, 
list_wf, 
length_of_nil_lemma, 
stuck-spread, 
base_wf, 
null_nil_lemma, 
btrue_wf, 
member-implies-null-eq-bfalse, 
nil_wf, 
btrue_neq_bfalse, 
length_nil, 
non_neg_length, 
int_seg_properties, 
satisfiable-full-omega-tt, 
intformand_wf, 
intformle_wf, 
itermConstant_wf, 
itermVar_wf, 
intformless_wf, 
int_formula_prop_and_lemma, 
int_formula_prop_le_lemma, 
int_term_value_constant_lemma, 
int_term_value_var_lemma, 
int_formula_prop_less_lemma, 
int_formula_prop_wf, 
list_ind_cons_lemma, 
length_of_cons_lemma, 
eq_int_wf, 
bool_wf, 
eqtt_to_assert, 
assert_of_eq_int, 
add_nat_plus, 
length_wf_nat, 
nat_plus_wf, 
nat_plus_properties, 
decidable__lt, 
add-is-int-iff, 
intformnot_wf, 
itermAdd_wf, 
intformeq_wf, 
int_formula_prop_not_lemma, 
int_term_value_add_lemma, 
int_formula_prop_eq_lemma, 
false_wf, 
equal_wf, 
cons_wf, 
cons_member, 
subtype_base_sq, 
eqff_to_assert, 
bool_cases_sqequal, 
bool_subtype_base, 
assert-bnot, 
neg_assert_of_eq_int, 
select-cons-tl, 
int_seg_subtype_nat, 
add-subtract-cancel
Rules used in proof : 
sqequalSubstitution, 
sqequalTransitivity, 
computationStep, 
sqequalReflexivity, 
lambdaFormation, 
cut, 
thin, 
introduction, 
extract_by_obid, 
sqequalHypSubstitution, 
isectElimination, 
intEquality, 
sqequalRule, 
lambdaEquality, 
productEquality, 
hypothesisEquality, 
hypothesis, 
applyEquality, 
setElimination, 
rename, 
natural_numberEquality, 
addEquality, 
functionEquality, 
baseApply, 
closedConclusion, 
baseClosed, 
because_Cache, 
independent_isectElimination, 
productElimination, 
independent_functionElimination, 
dependent_functionElimination, 
isect_memberEquality, 
voidElimination, 
voidEquality, 
independent_pairFormation, 
equalityTransitivity, 
equalitySymmetry, 
applyLambdaEquality, 
dependent_pairFormation, 
int_eqEquality, 
computeAll, 
unionElimination, 
equalityElimination, 
dependent_set_memberEquality, 
imageMemberEquality, 
pointwiseFunctionality, 
promote_hyp, 
inlFormation, 
instantiate, 
cumulativity, 
imageElimination, 
inrFormation
Latex:
\mforall{}x:\mBbbZ{}.  \mforall{}L:\mBbbZ{}  List.
    (((x  \mmember{}  L)  \mLeftarrow{}{}\mRightarrow{}  int-list-index(L;x)  <  ||L||)  \mwedge{}  ((x  \mmember{}  L)  {}\mRightarrow{}  (L[int-list-index(L;x)]  =  x)))
Date html generated:
2018_05_21-PM-07_32_24
Last ObjectModification:
2017_07_26-PM-05_07_31
Theory : general
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