Nuprl Lemma : fun-connected-step-back
∀[T:Type]. ∀f:T ⟶ T. ∀x,y:T.  (x is f*(y) 
⇒ x is f*(f y) supposing ¬(x = y ∈ T))
Proof
Definitions occuring in Statement : 
fun-connected: y is f*(x)
, 
uimplies: b supposing a
, 
uall: ∀[x:A]. B[x]
, 
all: ∀x:A. B[x]
, 
not: ¬A
, 
implies: P 
⇒ Q
, 
apply: f a
, 
function: x:A ⟶ B[x]
, 
universe: Type
, 
equal: s = t ∈ T
Definitions unfolded in proof : 
uall: ∀[x:A]. B[x]
, 
all: ∀x:A. B[x]
, 
implies: P 
⇒ Q
, 
uimplies: b supposing a
, 
member: t ∈ T
, 
not: ¬A
, 
false: False
, 
fun-connected: y is f*(x)
, 
exists: ∃x:A. B[x]
, 
or: P ∨ Q
, 
fun-path: y=f*(x) via L
, 
select: L[n]
, 
nil: []
, 
it: ⋅
, 
so_lambda: λ2x y.t[x; y]
, 
so_apply: x[s1;s2]
, 
subtract: n - m
, 
assert: ↑b
, 
ifthenelse: if b then t else f fi 
, 
btrue: tt
, 
and: P ∧ Q
, 
less_than: a < b
, 
squash: ↓T
, 
less_than': less_than'(a;b)
, 
cons: [a / b]
, 
bfalse: ff
, 
prop: ℙ
, 
append: as @ bs
, 
so_lambda: so_lambda3, 
so_apply: x[s1;s2;s3]
, 
ge: i ≥ j 
, 
true: True
, 
guard: {T}
, 
nat: ℕ
, 
le: A ≤ B
, 
cand: A c∧ B
, 
decidable: Dec(P)
, 
iff: P 
⇐⇒ Q
, 
rev_implies: P 
⇐ Q
, 
uiff: uiff(P;Q)
, 
listp: A List+
, 
subtype_rel: A ⊆r B
, 
satisfiable_int_formula: satisfiable_int_formula(fmla)
, 
int_seg: {i..j-}
, 
lelt: i ≤ j < k
, 
last: last(L)
, 
sq_type: SQType(T)
Lemmas referenced : 
list-cases, 
length_of_nil_lemma, 
stuck-spread, 
istype-base, 
null_nil_lemma, 
product_subtype_list, 
length_of_cons_lemma, 
reduce_hd_cons_lemma, 
null_cons_lemma, 
istype-void, 
fun-connected_wf, 
istype-universe, 
last_lemma, 
fun-path_wf, 
list_ind_nil_lemma, 
last_wf, 
hd_wf, 
squash_wf, 
ge_wf, 
length_wf, 
list_wf, 
listp_properties, 
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, 
cons_wf, 
nil_wf, 
member-less_than, 
append_wf, 
length_nil, 
non_neg_length, 
length_cons, 
length_append, 
subtype_rel_list, 
top_wf, 
length-append, 
full-omega-unsat, 
intformand_wf, 
intformnot_wf, 
intformless_wf, 
itermConstant_wf, 
itermAdd_wf, 
itermVar_wf, 
intformle_wf, 
istype-int, 
int_formula_prop_and_lemma, 
int_formula_prop_not_lemma, 
int_formula_prop_less_lemma, 
int_term_value_constant_lemma, 
int_term_value_add_lemma, 
int_term_value_var_lemma, 
int_formula_prop_le_lemma, 
int_formula_prop_wf, 
hd-append-sq, 
cons-listp, 
int_seg_wf, 
subtract_wf, 
list_ind_cons_lemma, 
decidable__le, 
add-is-int-iff, 
itermSubtract_wf, 
int_term_value_subtract_lemma, 
false_wf, 
istype-le, 
equal_wf, 
true_wf, 
select_wf, 
select_append_front, 
subtype_rel_self, 
iff_weakening_equal, 
subtype_base_sq, 
int_subtype_base, 
general_arith_equation1, 
length-singleton, 
int_seg_properties, 
select-nthtl0, 
int_seg_subtype_nat
Rules used in proof : 
sqequalSubstitution, 
sqequalTransitivity, 
computationStep, 
sqequalReflexivity, 
isect_memberFormation_alt, 
lambdaFormation_alt, 
cut, 
introduction, 
sqequalRule, 
sqequalHypSubstitution, 
lambdaEquality_alt, 
dependent_functionElimination, 
thin, 
hypothesisEquality, 
voidElimination, 
functionIsTypeImplies, 
inhabitedIsType, 
rename, 
productElimination, 
extract_by_obid, 
isectElimination, 
hypothesis, 
unionElimination, 
baseClosed, 
independent_isectElimination, 
Error :memTop, 
imageElimination, 
promote_hyp, 
hypothesis_subsumption, 
functionIsType, 
equalityIstype, 
universeIsType, 
because_Cache, 
instantiate, 
universeEquality, 
dependent_pairFormation_alt, 
applyEquality, 
independent_functionElimination, 
equalityTransitivity, 
equalitySymmetry, 
natural_numberEquality, 
setElimination, 
independent_pairFormation, 
addEquality, 
minusEquality, 
dependent_set_memberEquality_alt, 
imageMemberEquality, 
independent_pairEquality, 
axiomEquality, 
hyp_replacement, 
applyLambdaEquality, 
voidEquality, 
approximateComputation, 
int_eqEquality, 
pointwiseFunctionality, 
baseApply, 
closedConclusion, 
productIsType, 
cumulativity, 
intEquality
Latex:
\mforall{}[T:Type].  \mforall{}f:T  {}\mrightarrow{}  T.  \mforall{}x,y:T.    (x  is  f*(y)  {}\mRightarrow{}  x  is  f*(f  y)  supposing  \mneg{}(x  =  y))
Date html generated:
2020_05_20-AM-08_10_38
Last ObjectModification:
2019_12_31-PM-06_30_08
Theory : general
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