Nuprl Lemma : round-robin-list-index
∀[T:Type]. ∀[eq:EqDecider(T)]. ∀[x:T]. ∀[L:T List].  (round-robin(L) outl(list-index(eq;L;x))) = x ∈ T supposing (x ∈ L)
Proof
Definitions occuring in Statement : 
round-robin: round-robin(L), 
list-index: list-index(d;L;x), 
l_member: (x ∈ l), 
list: T List, 
deq: EqDecider(T), 
outl: outl(x), 
uimplies: b supposing a, 
uall: ∀[x:A]. B[x], 
apply: f a, 
universe: Type, 
equal: s = t ∈ T
Definitions unfolded in proof : 
uall: ∀[x:A]. B[x], 
member: t ∈ T, 
uimplies: b supposing a, 
round-robin: round-robin(L), 
all: ∀x:A. B[x], 
iff: P ⇐⇒ Q, 
and: P ∧ Q, 
rev_implies: P ⇐ Q, 
implies: P ⇒ Q, 
nat_plus: ℕ+, 
or: P ∨ Q, 
false: False, 
cons: [a / b], 
top: Top, 
guard: {T}, 
nat: ℕ, 
le: A ≤ B, 
cand: A c∧ B, 
decidable: Dec(P), 
not: ¬A, 
uiff: uiff(P;Q), 
subtract: n - m, 
less_than': less_than'(a;b), 
true: True, 
ge: i ≥ j , 
outl: outl(x), 
int_seg: {i..j-}, 
isl: isl(x), 
lelt: i ≤ j < k, 
satisfiable_int_formula: satisfiable_int_formula(fmla), 
exists: ∃x:A. B[x], 
prop: ℙ, 
sq_type: SQType(T)
Lemmas referenced : 
list-index-property, 
subtype_base_sq, 
int_subtype_base, 
rem_base_case, 
outl_wf, 
isl-list-index, 
length_wf, 
list-cases, 
length_of_nil_lemma, 
nil_member, 
product_subtype_list, 
length_of_cons_lemma, 
istype-void, 
length_wf_nat, 
decidable__lt, 
istype-false, 
not-lt-2, 
condition-implies-le, 
minus-add, 
minus-one-mul, 
zero-add, 
minus-one-mul-top, 
add-commutes, 
add_functionality_wrt_le, 
add-associates, 
add-zero, 
le-add-cancel, 
istype-less_than, 
non_neg_length, 
assert_elim, 
btrue_wf, 
bfalse_wf, 
btrue_neq_bfalse, 
nat_properties, 
int_seg_properties, 
full-omega-unsat, 
intformand_wf, 
intformless_wf, 
itermVar_wf, 
intformnot_wf, 
istype-int, 
int_formula_prop_and_lemma, 
int_formula_prop_less_lemma, 
int_term_value_var_lemma, 
int_formula_prop_not_lemma, 
int_formula_prop_wf, 
l_member_wf, 
list_wf, 
deq_wf, 
istype-universe
Rules used in proof : 
cut, 
introduction, 
extract_by_obid, 
sqequalSubstitution, 
sqequalTransitivity, 
computationStep, 
sqequalReflexivity, 
Error :isect_memberFormation_alt, 
hypothesis, 
sqequalHypSubstitution, 
isectElimination, 
thin, 
hypothesisEquality, 
independent_isectElimination, 
sqequalRule, 
instantiate, 
cumulativity, 
intEquality, 
because_Cache, 
dependent_functionElimination, 
productElimination, 
independent_functionElimination, 
Error :dependent_set_memberEquality_alt, 
unionElimination, 
voidElimination, 
promote_hyp, 
hypothesis_subsumption, 
Error :isect_memberEquality_alt, 
Error :inhabitedIsType, 
Error :lambdaFormation_alt, 
setElimination, 
rename, 
independent_pairFormation, 
natural_numberEquality, 
addEquality, 
minusEquality, 
Error :equalityIstype, 
equalityTransitivity, 
equalitySymmetry, 
Error :productIsType, 
applyLambdaEquality, 
approximateComputation, 
Error :dependent_pairFormation_alt, 
Error :lambdaEquality_alt, 
int_eqEquality, 
Error :universeIsType, 
universeEquality
Latex:
\mforall{}[T:Type].  \mforall{}[eq:EqDecider(T)].  \mforall{}[x:T].  \mforall{}[L:T  List].
    (round-robin(L)  outl(list-index(eq;L;x)))  =  x  supposing  (x  \mmember{}  L)
Date html generated:
2019_06_20-PM-01_56_52
Last ObjectModification:
2019_03_06-AM-10_52_27
Theory : decidable!equality
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