Nuprl Lemma : cons-sub-co-list-cons
∀[T:Type]
  ∀x1,x2:T. ∀L1,L2:colist(T).
    (sub-co-list(T;[x1 / L1];[x2 / L2]) ⇐⇒ ((x1 = x2 ∈ T) ∧ sub-co-list(T;L1;L2)) ∨ sub-co-list(T;[x1 / L1];L2))
Proof
Definitions occuring in Statement : 
sub-co-list: sub-co-list(T;s1;s2), 
cons: [a / b], 
colist: colist(T), 
uall: ∀[x:A]. B[x], 
all: ∀x:A. B[x], 
iff: P ⇐⇒ Q, 
or: P ∨ Q, 
and: P ∧ Q, 
universe: Type, 
equal: s = t ∈ T
Definitions unfolded in proof : 
cons: [a / b], 
co-cons: [x / L], 
uall: ∀[x:A]. B[x], 
all: ∀x:A. B[x], 
iff: P ⇐⇒ Q, 
and: P ∧ Q, 
implies: P ⇒ Q, 
member: t ∈ T, 
prop: ℙ, 
rev_implies: P ⇐ Q, 
or: P ∨ Q, 
sub-co-list: sub-co-list(T;s1;s2), 
exists: ∃x:A. B[x], 
ext-eq: A ≡ B, 
subtype_rel: A ⊆r B, 
bool: 𝔹, 
unit: Unit, 
it: ⋅, 
btrue: tt, 
uimplies: b supposing a, 
nil: [], 
list-at: L1@L2, 
top: Top, 
ifthenelse: if b then t else f fi , 
bfalse: ff, 
co-nil: (), 
uiff: uiff(P;Q), 
false: False, 
nat: ℕ, 
decidable: Dec(P), 
not: ¬A, 
guard: {T}, 
ge: i ≥ j , 
satisfiable_int_formula: satisfiable_int_formula(fmla), 
rev_uimplies: rev_uimplies(P;Q), 
sq_type: SQType(T), 
bnot: ¬bb, 
assert: ↑b, 
nequal: a ≠ b ∈ T , 
subtract: n - m
Lemmas referenced : 
sub-co-list_wf, 
co-cons_wf, 
colist_wf, 
istype-universe, 
colist-ext, 
nat_wf, 
isaxiom_wf_listunion, 
subtype_rel_b-union-left, 
unit_wf2, 
axiom-listunion, 
null_nil_lemma, 
null_cons_lemma, 
istype-void, 
reduce_hd_cons_lemma, 
reduce_tl_cons_lemma, 
reduce_tl_nil_lemma, 
subtype_rel_b-union-right, 
non-axiom-listunion, 
co-cons-not-co-nil, 
decidable__equal_int, 
co-cons_one_one, 
list-at_wf, 
subtract_wf, 
nat_properties, 
decidable__le, 
full-omega-unsat, 
intformand_wf, 
intformnot_wf, 
intformle_wf, 
itermConstant_wf, 
itermSubtract_wf, 
itermVar_wf, 
intformeq_wf, 
istype-int, 
int_formula_prop_and_lemma, 
int_formula_prop_not_lemma, 
int_formula_prop_le_lemma, 
int_term_value_constant_lemma, 
int_term_value_subtract_lemma, 
int_term_value_var_lemma, 
int_formula_prop_eq_lemma, 
int_formula_prop_wf, 
istype-le, 
list_at_nil2_lemma, 
itermAdd_wf, 
int_term_value_add_lemma, 
eq_int_wf, 
eqtt_to_assert, 
assert_of_eq_int, 
eqff_to_assert, 
bool_cases_sqequal, 
subtype_base_sq, 
bool_wf, 
bool_subtype_base, 
assert-bnot, 
neg_assert_of_eq_int, 
int_subtype_base
Rules used in proof : 
sqequalSubstitution, 
sqequalRule, 
sqequalReflexivity, 
sqequalTransitivity, 
computationStep, 
Error :isect_memberFormation_alt, 
Error :lambdaFormation_alt, 
independent_pairFormation, 
Error :universeIsType, 
cut, 
introduction, 
extract_by_obid, 
sqequalHypSubstitution, 
isectElimination, 
thin, 
hypothesisEquality, 
hypothesis, 
Error :unionIsType, 
Error :productIsType, 
Error :equalityIstype, 
Error :inhabitedIsType, 
instantiate, 
universeEquality, 
productElimination, 
promote_hyp, 
hypothesis_subsumption, 
applyEquality, 
unionElimination, 
equalityElimination, 
productEquality, 
independent_isectElimination, 
dependent_functionElimination, 
Error :isect_memberEquality_alt, 
voidElimination, 
rename, 
equalityTransitivity, 
equalitySymmetry, 
independent_functionElimination, 
setElimination, 
natural_numberEquality, 
int_eqReduceTrueSq, 
int_eqReduceFalseSq, 
Error :inlFormation_alt, 
Error :dependent_pairFormation_alt, 
Error :inrFormation_alt, 
Error :dependent_set_memberEquality_alt, 
approximateComputation, 
Error :lambdaEquality_alt, 
int_eqEquality, 
addEquality, 
cumulativity, 
because_Cache, 
intEquality, 
minusEquality
Latex:
\mforall{}[T:Type]
    \mforall{}x1,x2:T.  \mforall{}L1,L2:colist(T).
        (sub-co-list(T;[x1  /  L1];[x2  /  L2])
        \mLeftarrow{}{}\mRightarrow{}  ((x1  =  x2)  \mwedge{}  sub-co-list(T;L1;L2))  \mvee{}  sub-co-list(T;[x1  /  L1];L2))
 Date html generated: 
2019_06_20-PM-01_22_16
 Last ObjectModification: 
2019_01_02-PM-05_35_39
Theory : list_1
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