Nuprl Lemma : extensional-discrete-real-fun-is-constant
∀a,b:ℝ. ∀f:{x:ℝ| x ∈ [a, b]}  ⟶ ℤ.
  ∀x,y:{x:ℝ| x ∈ [a, b]} .  ((f x) = (f y) ∈ ℤ) supposing ∀x,y:{x:ℝ| x ∈ [a, b]} .  ((x = y) ⇒ ((f x) = (f y) ∈ ℤ))
Proof
Definitions occuring in Statement : 
rccint: [l, u], 
i-member: r ∈ I, 
req: x = y, 
real: ℝ, 
uimplies: b supposing a, 
all: ∀x:A. B[x], 
implies: P ⇒ Q, 
set: {x:A| B[x]} , 
apply: f a, 
function: x:A ⟶ B[x], 
int: ℤ, 
equal: s = t ∈ T
Definitions unfolded in proof : 
all: ∀x:A. B[x], 
member: t ∈ T, 
uimplies: b supposing a, 
top: Top, 
and: P ∧ Q, 
uall: ∀[x:A]. B[x], 
guard: {T}, 
rfun: I ⟶ℝ, 
prop: ℙ, 
iff: P ⇐⇒ Q, 
implies: P ⇒ Q, 
real-fun: real-fun(f;a;b), 
uiff: uiff(P;Q), 
so_lambda: λ2x.t[x], 
so_apply: x[s], 
real-cont: real-cont(f;a;b), 
nat_plus: ℕ+, 
less_than: a < b, 
squash: ↓T, 
less_than': less_than'(a;b), 
true: True, 
exists: ∃x:A. B[x], 
decidable: Dec(P), 
or: P ∨ Q, 
false: False, 
not: ¬A, 
satisfiable_int_formula: satisfiable_int_formula(fmla), 
rneq: x ≠ y, 
rev_implies: P ⇐ Q, 
le: A ≤ B, 
rleq: x ≤ y, 
rnonneg: rnonneg(x), 
subtype_rel: A ⊆r B, 
nat: ℕ, 
rdiv: (x/y), 
req_int_terms: t1 ≡ t2, 
int_seg: {i..j-}, 
lelt: i ≤ j < k, 
ge: i ≥ j , 
rless: x < y, 
sq_exists: ∃x:{A| B[x]}, 
sq_type: SQType(T), 
real: ℝ, 
sq_stable: SqStable(P), 
rbetween: x≤y≤z, 
rev_uimplies: rev_uimplies(P;Q), 
i-member: r ∈ I, 
rccint: [l, u], 
label: ...$L... t, 
full-partition: full-partition(I;p), 
partition: partition(I)
Lemmas referenced : 
real-fun-iff-continuous, 
member_rccint_lemma, 
rleq_transitivity, 
int-to-real_wf, 
real_wf, 
rleq_wf, 
i-member_wf, 
rccint_wf, 
req-int, 
req_wf, 
set_wf, 
all_wf, 
equal_wf, 
less_than_wf, 
rabs_wf, 
rsub_wf, 
decidable__equal_int, 
subtract-is-int-iff, 
full-omega-unsat, 
intformand_wf, 
intformnot_wf, 
intformeq_wf, 
itermVar_wf, 
itermSubtract_wf, 
itermConstant_wf, 
int_formula_prop_and_lemma, 
int_formula_prop_not_lemma, 
int_formula_prop_eq_lemma, 
int_term_value_var_lemma, 
int_term_value_subtract_lemma, 
int_term_value_constant_lemma, 
int_formula_prop_wf, 
false_wf, 
subtract_wf, 
rdiv_wf, 
rless-int, 
rless_wf, 
rleq_functionality, 
rabs_functionality, 
rsub-int, 
req_weakening, 
rmul_preserves_rleq2, 
rleq-int, 
less_than'_wf, 
rmul_wf, 
nat_plus_wf, 
absval_wf, 
nat_wf, 
itermMultiply_wf, 
rinv_wf2, 
req_transitivity, 
squash_wf, 
true_wf, 
rabs-int, 
rmul-int, 
rmul-rinv, 
req-iff-rsub-is-0, 
real_polynomial_null, 
real_term_value_sub_lemma, 
real_term_value_mul_lemma, 
real_term_value_var_lemma, 
real_term_value_const_lemma, 
absval_unfold, 
decidable__lt, 
top_wf, 
intformless_wf, 
intformle_wf, 
int_formula_prop_less_lemma, 
int_formula_prop_le_lemma, 
int_term_value_mul_lemma, 
itermMinus_wf, 
int_term_value_minus_lemma, 
partition-exists, 
rccint-icompact, 
list_set_type, 
full-partition_wf, 
full-partition-point-member, 
mesh-property, 
int_seg_properties, 
length_wf, 
int_seg_wf, 
le_wf, 
nat_properties, 
ge_wf, 
decidable__le, 
select_wf, 
nat_plus_properties, 
subtype_base_sq, 
int_subtype_base, 
sq_stable__less_than, 
adjacent-full-partition-points, 
lelt_wf, 
subtract-add-cancel, 
rbetween_wf, 
partition-mesh_wf, 
rabs-of-nonneg, 
sq_stable__rleq, 
iff_weakening_equal, 
length_of_cons_lemma, 
right_endpoint_rccint_lemma, 
add_nat_plus, 
length_wf_nat, 
append_wf, 
cons_wf, 
nil_wf, 
length-append, 
length_of_nil_lemma, 
add-is-int-iff, 
itermAdd_wf, 
int_term_value_add_lemma
Rules used in proof : 
cut, 
introduction, 
extract_by_obid, 
sqequalSubstitution, 
sqequalTransitivity, 
computationStep, 
sqequalReflexivity, 
lambdaFormation, 
hypothesis, 
sqequalHypSubstitution, 
dependent_functionElimination, 
thin, 
hypothesisEquality, 
isect_memberFormation, 
setElimination, 
rename, 
isect_memberEquality, 
voidElimination, 
voidEquality, 
sqequalRule, 
independent_isectElimination, 
productElimination, 
isectElimination, 
lambdaEquality, 
applyEquality, 
functionExtensionality, 
setEquality, 
productEquality, 
independent_functionElimination, 
dependent_set_memberEquality, 
axiomEquality, 
because_Cache, 
functionEquality, 
intEquality, 
natural_numberEquality, 
independent_pairFormation, 
imageMemberEquality, 
baseClosed, 
unionElimination, 
pointwiseFunctionality, 
equalityTransitivity, 
equalitySymmetry, 
promote_hyp, 
baseApply, 
closedConclusion, 
approximateComputation, 
dependent_pairFormation, 
int_eqEquality, 
inrFormation, 
independent_pairEquality, 
minusEquality, 
multiplyEquality, 
imageElimination, 
lessCases, 
sqequalAxiom, 
intWeakElimination, 
instantiate, 
cumulativity, 
addEquality, 
universeEquality, 
applyLambdaEquality
Latex:
\mforall{}a,b:\mBbbR{}.  \mforall{}f:\{x:\mBbbR{}|  x  \mmember{}  [a,  b]\}    {}\mrightarrow{}  \mBbbZ{}.
    \mforall{}x,y:\{x:\mBbbR{}|  x  \mmember{}  [a,  b]\}  .    ((f  x)  =  (f  y)) 
    supposing  \mforall{}x,y:\{x:\mBbbR{}|  x  \mmember{}  [a,  b]\}  .    ((x  =  y)  {}\mRightarrow{}  ((f  x)  =  (f  y)))
Date html generated:
2017_10_03-AM-09_59_57
Last ObjectModification:
2017_06_01-PM-04_32_03
Theory : reals
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