Nuprl Lemma : adjacent-append
∀[T:Type]
  ∀x,y:T. ∀L1,L2:T List.
    (adjacent(T;L1 @ L2;x;y)
    
⇐⇒ adjacent(T;L1;x;y) ∨ (0 < ||L1|| ∧ 0 < ||L2|| ∧ (x = last(L1) ∈ T) ∧ (y = hd(L2) ∈ T)) ∨ adjacent(T;L2;x;y))
Proof
Definitions occuring in Statement : 
adjacent: adjacent(T;L;x;y)
, 
last: last(L)
, 
length: ||as||
, 
append: as @ bs
, 
hd: hd(l)
, 
list: T List
, 
less_than: a < b
, 
uall: ∀[x:A]. B[x]
, 
all: ∀x:A. B[x]
, 
iff: P 
⇐⇒ Q
, 
or: P ∨ Q
, 
and: P ∧ Q
, 
natural_number: $n
, 
universe: Type
, 
equal: s = t ∈ T
Definitions unfolded in proof : 
adjacent: adjacent(T;L;x;y)
, 
uall: ∀[x:A]. B[x]
, 
all: ∀x:A. B[x]
, 
iff: P 
⇐⇒ Q
, 
and: P ∧ Q
, 
implies: P 
⇒ Q
, 
exists: ∃x:A. B[x]
, 
member: t ∈ T
, 
int_seg: {i..j-}
, 
uimplies: b supposing a
, 
top: Top
, 
guard: {T}
, 
lelt: i ≤ j < k
, 
decidable: Dec(P)
, 
or: P ∨ Q
, 
not: ¬A
, 
satisfiable_int_formula: satisfiable_int_formula(fmla)
, 
false: False
, 
prop: ℙ
, 
less_than: a < b
, 
squash: ↓T
, 
uiff: uiff(P;Q)
, 
rev_implies: P 
⇐ Q
, 
assert: ↑b
, 
ifthenelse: if b then t else f fi 
, 
btrue: tt
, 
less_than': less_than'(a;b)
, 
cons: [a / b]
, 
bfalse: ff
, 
ge: i ≥ j 
, 
subtract: n - m
, 
append: as @ bs
, 
so_lambda: so_lambda(x,y,z.t[x; y; z])
, 
so_apply: x[s1;s2;s3]
, 
true: True
, 
subtype_rel: A ⊆r B
, 
cand: A c∧ B
, 
le: A ≤ B
, 
last: last(L)
, 
select: L[n]
, 
nil: []
, 
it: ⋅
, 
so_lambda: λ2x y.t[x; y]
, 
so_apply: x[s1;s2]
, 
sq_type: SQType(T)
Lemmas referenced : 
int_seg_wf, 
subtract_wf, 
length_wf, 
append_wf, 
select_wf, 
length-append, 
istype-void, 
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, 
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, 
subtract-is-int-iff, 
add-is-int-iff, 
intformless_wf, 
itermAdd_wf, 
itermSubtract_wf, 
int_formula_prop_less_lemma, 
int_term_value_add_lemma, 
int_term_value_subtract_lemma, 
false_wf, 
istype-less_than, 
last_wf, 
list-cases, 
null_nil_lemma, 
length_of_nil_lemma, 
product_subtype_list, 
null_cons_lemma, 
length_of_cons_lemma, 
hd_wf, 
list_wf, 
istype-universe, 
list_ind_nil_lemma, 
equal_wf, 
squash_wf, 
true_wf, 
select_append_front, 
istype-le, 
subtype_rel_self, 
iff_weakening_equal, 
add-member-int_seg2, 
select_append_back, 
non_neg_length, 
length_append, 
subtype_rel_list, 
top_wf, 
le_wf, 
less_than_wf, 
decidable__equal_int, 
intformeq_wf, 
int_formula_prop_eq_lemma, 
stuck-spread, 
istype-base, 
subtype_base_sq, 
int_subtype_base, 
reduce_hd_cons_lemma, 
general_arith_equation1, 
add-associates, 
add-swap, 
add-commutes, 
zero-add, 
select-nthtl, 
length_wf_nat, 
nth_tl_append, 
add-member-int_seg1, 
minus-one-mul, 
add-mul-special, 
zero-mul, 
add-zero
Rules used in proof : 
sqequalSubstitution, 
sqequalRule, 
sqequalReflexivity, 
sqequalTransitivity, 
computationStep, 
isect_memberFormation_alt, 
lambdaFormation_alt, 
independent_pairFormation, 
sqequalHypSubstitution, 
productElimination, 
thin, 
productIsType, 
universeIsType, 
cut, 
introduction, 
extract_by_obid, 
isectElimination, 
natural_numberEquality, 
hypothesisEquality, 
hypothesis, 
equalityIsType1, 
inhabitedIsType, 
because_Cache, 
setElimination, 
rename, 
independent_isectElimination, 
isect_memberEquality_alt, 
voidElimination, 
addEquality, 
dependent_functionElimination, 
unionElimination, 
approximateComputation, 
independent_functionElimination, 
dependent_pairFormation_alt, 
lambdaEquality_alt, 
int_eqEquality, 
pointwiseFunctionality, 
equalityTransitivity, 
equalitySymmetry, 
promote_hyp, 
imageElimination, 
baseApply, 
closedConclusion, 
baseClosed, 
unionIsType, 
hypothesis_subsumption, 
instantiate, 
universeEquality, 
inlFormation_alt, 
applyEquality, 
dependent_set_memberEquality_alt, 
imageMemberEquality, 
minusEquality, 
inrFormation_alt, 
productEquality, 
hyp_replacement, 
applyLambdaEquality, 
cumulativity, 
intEquality
Latex:
\mforall{}[T:Type]
    \mforall{}x,y:T.  \mforall{}L1,L2:T  List.
        (adjacent(T;L1  @  L2;x;y)
        \mLeftarrow{}{}\mRightarrow{}  adjacent(T;L1;x;y)
                \mvee{}  (0  <  ||L1||  \mwedge{}  0  <  ||L2||  \mwedge{}  (x  =  last(L1))  \mwedge{}  (y  =  hd(L2)))
                \mvee{}  adjacent(T;L2;x;y))
Date html generated:
2019_10_15-AM-11_08_21
Last ObjectModification:
2018_10_18-PM-11_52_15
Theory : general
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