Nuprl Lemma : length-list-delete
∀[T:Type]. ∀[as:T List]. ∀[i:ℕ].  ||as\i|| = (||as|| - 1) ∈ ℤ supposing i < ||as||
Proof
Definitions occuring in Statement : 
list-delete: as\i, 
length: ||as||, 
list: T List, 
nat: ℕ, 
less_than: a < b, 
uimplies: b supposing a, 
uall: ∀[x:A]. B[x], 
subtract: n - m, 
natural_number: $n, 
int: ℤ, 
universe: Type, 
equal: s = t ∈ T
Definitions unfolded in proof : 
uall: ∀[x:A]. B[x], 
member: t ∈ T, 
so_lambda: λ2x.t[x], 
uimplies: b supposing a, 
nat: ℕ, 
prop: ℙ, 
so_apply: x[s], 
implies: P ⇒ Q, 
list-delete: as\i, 
nil: [], 
it: ⋅, 
subtract: n - m, 
all: ∀x:A. B[x], 
cons: [a / b], 
top: Top, 
so_lambda: λ2x y.t[x; y], 
so_apply: x[s1;s2], 
false: False, 
guard: {T}, 
bool: 𝔹, 
unit: Unit, 
btrue: tt, 
uiff: uiff(P;Q), 
and: P ∧ Q, 
less_than: a < b, 
less_than': less_than'(a;b), 
true: True, 
squash: ↓T, 
not: ¬A, 
subtype_rel: A ⊆r B, 
bfalse: ff, 
exists: ∃x:A. B[x], 
or: P ∨ Q, 
sq_type: SQType(T), 
bnot: ¬bb, 
ifthenelse: if b then t else f fi , 
assert: ↑b, 
decidable: Dec(P), 
iff: P ⇐⇒ Q, 
rev_implies: P ⇐ Q, 
le: A ≤ B, 
nat_plus: ℕ+
Lemmas referenced : 
list_induction, 
uall_wf, 
nat_wf, 
isect_wf, 
less_than_wf, 
length_wf, 
equal_wf, 
list-delete_wf, 
subtract_wf, 
list_wf, 
length_of_nil_lemma, 
nil_wf, 
length_of_cons_lemma, 
spread_cons_lemma, 
cons_wf, 
less_than_transitivity1, 
less_than_irreflexivity, 
lt_int_wf, 
bool_wf, 
eqtt_to_assert, 
assert_of_lt_int, 
top_wf, 
add-associates, 
add-swap, 
add-commutes, 
zero-add, 
eqff_to_assert, 
bool_cases_sqequal, 
subtype_base_sq, 
bool_subtype_base, 
assert-bnot, 
decidable__le, 
false_wf, 
not-le-2, 
not-lt-2, 
condition-implies-le, 
minus-one-mul, 
minus-one-mul-top, 
minus-add, 
minus-minus, 
add_functionality_wrt_le, 
le-add-cancel, 
le_wf, 
non_neg_length, 
length_wf_nat, 
set_subtype_base, 
int_subtype_base, 
less-iff-le, 
le_reflexive, 
one-mul, 
add-mul-special, 
two-mul, 
mul-distributes-right, 
zero-mul, 
add-zero, 
omega-shadow, 
mul-distributes, 
mul-associates, 
mul-commutes, 
le-add-cancel-alt, 
squash_wf, 
true_wf, 
add_functionality_wrt_eq, 
iff_weakening_equal, 
nat_properties, 
decidable__lt
Rules used in proof : 
sqequalSubstitution, 
sqequalTransitivity, 
computationStep, 
sqequalReflexivity, 
isect_memberFormation, 
introduction, 
cut, 
thin, 
extract_by_obid, 
sqequalHypSubstitution, 
isectElimination, 
hypothesisEquality, 
sqequalRule, 
lambdaEquality, 
hypothesis, 
setElimination, 
rename, 
cumulativity, 
intEquality, 
because_Cache, 
natural_numberEquality, 
independent_functionElimination, 
voidEquality, 
isect_memberEquality, 
axiomEquality, 
equalityTransitivity, 
equalitySymmetry, 
lambdaFormation, 
dependent_functionElimination, 
voidElimination, 
universeEquality, 
independent_isectElimination, 
unionElimination, 
equalityElimination, 
productElimination, 
lessCases, 
sqequalAxiom, 
independent_pairFormation, 
imageMemberEquality, 
baseClosed, 
imageElimination, 
applyEquality, 
minusEquality, 
dependent_pairFormation, 
promote_hyp, 
instantiate, 
dependent_set_memberEquality, 
addEquality, 
sqequalIntensionalEquality, 
multiplyEquality
Latex:
\mforall{}[T:Type].  \mforall{}[as:T  List].  \mforall{}[i:\mBbbN{}].    ||as\mbackslash{}i||  =  (||as||  -  1)  supposing  i  <  ||as||
 Date html generated: 
2017_04_14-AM-08_55_37
 Last ObjectModification: 
2017_02_27-PM-03_39_30
Theory : omega
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