Nuprl Lemma : fset-size-remove
∀[T:Type]. ∀[eq:EqDecider(T)]. ∀[s:fset(T)]. ∀[x:T].  ||fset-remove(eq;x;s)|| = (||s|| - 1) ∈ ℤ supposing x ∈ s
Proof
Definitions occuring in Statement : 
fset-size: ||s||, 
fset-remove: fset-remove(eq;y;s), 
fset-member: a ∈ s, 
fset: fset(T), 
deq: EqDecider(T), 
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, 
uimplies: b supposing a, 
fset: fset(T), 
all: ∀x:A. B[x], 
prop: ℙ, 
quotient: x,y:A//B[x; y], 
and: P ∧ Q, 
squash: ↓T, 
subtype_rel: A ⊆r B, 
istype: istype(T), 
true: True, 
nat: ℕ, 
guard: {T}, 
iff: P ⇐⇒ Q, 
rev_implies: P ⇐ Q, 
implies: P ⇒ Q, 
fset-member: a ∈ s, 
fset-size: ||s||, 
fset-remove: fset-remove(eq;y;s), 
fset-filter: {x ∈ s | P[x]}, 
deq: EqDecider(T), 
or: P ∨ Q, 
so_lambda: λ2x.t[x], 
so_apply: x[s], 
not: ¬A, 
false: False, 
eqof: eqof(d), 
uiff: uiff(P;Q), 
rev_uimplies: rev_uimplies(P;Q), 
sq_type: SQType(T), 
cand: A c∧ B, 
remove-first: remove-first(P;L), 
so_lambda: so_lambda(x,y,z.t[x; y; z]), 
bool: 𝔹, 
unit: Unit, 
it: ⋅, 
btrue: tt, 
ifthenelse: if b then t else f fi , 
bfalse: ff, 
exists: ∃x:A. B[x], 
bnot: ¬bb, 
assert: ↑b, 
so_apply: x[s1;s2;s3], 
top: Top
Lemmas referenced : 
list_wf, 
set-equal_wf, 
set-equal-reflex, 
equal_wf, 
squash_wf, 
true_wf, 
fset-size_wf, 
fset-remove_wf, 
subtype_rel_self, 
istype-nat, 
fset_wf, 
iff_weakening_equal, 
subtract_wf, 
istype-int, 
fset-member_wf, 
deq_wf, 
istype-universe, 
assert-deq-member, 
bnot_wf, 
length_wf, 
remove-repeats_wf, 
length-remove-first, 
l_member_wf, 
remove-repeats-filter, 
l_all_iff, 
not_wf, 
assert_wf, 
member-remove-repeats, 
safe-assert-deq, 
subtype_base_sq, 
int_subtype_base, 
remove-repeats-no_repeats, 
list_induction, 
no_repeats_wf, 
filter_wf5, 
list_ind_wf, 
nil_wf, 
bool_wf, 
eqff_to_assert, 
bool_cases_sqequal, 
bool_subtype_base, 
assert-bnot, 
cons_wf, 
filter_nil_lemma, 
list_ind_nil_lemma, 
filter_cons_lemma, 
list_ind_cons_lemma, 
eqtt_to_assert, 
no_repeats_cons, 
cons_member, 
filter_trivial, 
iff_transitivity, 
eqof_wf, 
iff_weakening_uiff, 
assert_of_bnot, 
and_wf
Rules used in proof : 
sqequalSubstitution, 
sqequalTransitivity, 
computationStep, 
sqequalReflexivity, 
Error :isect_memberFormation_alt, 
introduction, 
cut, 
sqequalHypSubstitution, 
Error :universeIsType, 
extract_by_obid, 
isectElimination, 
thin, 
hypothesisEquality, 
hypothesis, 
promote_hyp, 
Error :lambdaFormation_alt, 
Error :inhabitedIsType, 
pointwiseFunctionality, 
sqequalRule, 
pertypeElimination, 
productElimination, 
Error :productIsType, 
Error :equalityIsType4, 
dependent_functionElimination, 
applyEquality, 
Error :lambdaEquality_alt, 
imageElimination, 
equalityTransitivity, 
equalitySymmetry, 
because_Cache, 
intEquality, 
natural_numberEquality, 
imageMemberEquality, 
baseClosed, 
setElimination, 
rename, 
independent_isectElimination, 
independent_functionElimination, 
closedConclusion, 
instantiate, 
universeEquality, 
Error :isect_memberEquality_alt, 
axiomEquality, 
Error :isectIsTypeImplies, 
Error :setIsType, 
unionElimination, 
voidElimination, 
cumulativity, 
independent_pairFormation, 
Error :equalityIsType1, 
lambdaFormation, 
lambdaEquality, 
functionEquality, 
productEquality, 
setEquality, 
equalityElimination, 
dependent_pairFormation, 
isect_memberEquality, 
voidEquality, 
addLevel, 
impliesFunctionality, 
hyp_replacement, 
dependent_set_memberEquality, 
applyLambdaEquality
Latex:
\mforall{}[T:Type].  \mforall{}[eq:EqDecider(T)].  \mforall{}[s:fset(T)].  \mforall{}[x:T].
    ||fset-remove(eq;x;s)||  =  (||s||  -  1)  supposing  x  \mmember{}  s
Date html generated:
2019_06_20-PM-01_59_48
Last ObjectModification:
2018_11_22-AM-10_00_28
Theory : finite!sets
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