Natural numbers with infinity #
The natural numbers and an extra top
element ⊤
. This implementation uses Part ℕ
as an
implementation. Use ℕ∞
instead unless you care about computability.
Main definitions #
The following instances are defined:
There is no additive analogue of MonoidWithZero
; if there were then PartENat
could
be an AddMonoidWithTop
.
-
toWithTop
: the map fromPartENat
toℕ∞
, with theorems that it plays well with+
and≤
. -
withTopAddEquiv : PartENat ≃+ ℕ∞
-
withTopOrderIso : PartENat ≃o ℕ∞
Implementation details #
PartENat
is defined to be Part ℕ
.
+
and ≤
are defined on PartENat
, but there is an issue with *
because it's not
clear what 0 * ⊤
should be. mul
is hence left undefined. Similarly ⊤ - ⊤
is ambiguous
so there is no -
defined on PartENat
.
Before the open Classical
line, various proofs are made with decidability assumptions.
This can cause issues -- see for example the non-simp lemma toWithTopZero
proved by rfl
,
followed by @[simp] lemma toWithTopZero'
whose proof uses convert
.
Tags #
PartENat, ℕ∞
The computable embedding ℕ → PartENat
.
This coincides with the coercion coe : ℕ → PartENat
, see PartENat.some_eq_natCast
.
Equations
- PartENat.some = Part.some
Instances For
Equations
- PartENat.instZeroPartENat = { zero := ↑0 }
Equations
- PartENat.instInhabitedPartENat = { default := 0 }
Equations
- PartENat.instOnePartENat = { one := ↑1 }
Equations
Equations
- PartENat.instAddCommMonoidWithOnePartENat = let src := PartENat.addCommMonoid; AddCommMonoidWithOne.mk (_ : ∀ (a b : PartENat), a + b = b + a)
Alias of Nat.cast_inj
specialized to PartENat
-
Equations
- PartENat.instLEPartENat = { le := fun (x y : PartENat) => ∃ (h : y.Dom → x.Dom), ∀ (hy : y.Dom), x.get (_ : x.Dom) ≤ y.get hy }
Equations
- PartENat.instTopPartENat = { top := Part.none }
Equations
- PartENat.instBotPartENat = { bot := 0 }
Equations
Alias of Nat.cast_le
specialized to PartENat
-
Alias of Nat.cast_lt
specialized to PartENat
-
Equations
- One or more equations did not get rendered due to their size.
Equations
- PartENat.boundedOrder = let src := PartENat.orderTop; let src_1 := PartENat.orderBot; BoundedOrder.mk
Equations
- One or more equations did not get rendered due to their size.
Equations
- One or more equations did not get rendered due to their size.
Equations
- PartENat.instCoeENatPartENat = { coe := PartENat.ofENat }
Equiv
between PartENat
and ℕ∞
(for the order isomorphism see
withTopOrderIso
).
Equations
- One or more equations did not get rendered due to their size.
Instances For
to_WithTop
induces an order isomorphism between PartENat
and ℕ∞
.
Equations
- PartENat.withTopOrderIso = let src := PartENat.withTopEquiv; { toEquiv := src, map_rel_iff' := (_ : ∀ (x x_1 : PartENat), PartENat.withTopEquiv x ≤ PartENat.withTopEquiv x_1 ↔ x ≤ x_1) }
Instances For
toWithTop
induces an additive monoid isomorphism between PartENat
and ℕ∞
.
Equations
- PartENat.withTopAddEquiv = let src := PartENat.withTopEquiv; { toEquiv := src, map_add' := PartENat.withTopAddEquiv.proof_1 }
Instances For
Equations
- PartENat.instWellFoundedLTPartENatToLTToPreorderPartialOrder = (_ : IsWellFounded PartENat fun (x x_1 : PartENat) => x < x_1)
Equations
- PartENat.isWellOrder = (_ : IsWellOrder PartENat fun (x x_1 : PartENat) => x < x_1)
Equations
- PartENat.wellFoundedRelation = { rel := fun (x x_1 : PartENat) => x < x_1, wf := PartENat.lt_wf }
The smallest PartENat
satisfying a (decidable) predicate P : ℕ → Prop
Equations
- PartENat.find P = { Dom := ∃ (n : ℕ), P n, get := Nat.find }
Instances For
Equations
- One or more equations did not get rendered due to their size.
Equations
- One or more equations did not get rendered due to their size.