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docs: AddCircle instead of add_circle in docstrings (#4035)
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pechersky committed May 16, 2023
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54 changes: 27 additions & 27 deletions Mathlib/Topology/Instances/AddCircle.lean
Expand Up @@ -19,35 +19,35 @@ import Mathlib.Topology.Instances.Real
/-!
# The additive circle
We define the additive circle `add_circle p` as the quotient `π•œ β§Έ (β„€ βˆ™ p)` for some period `p : π•œ`.
We define the additive circle `AddCircle p` as the quotient `π•œ β§Έ (β„€ βˆ™ p)` for some period `p : π•œ`.
See also `circle` and `real.angle`. For the normed group structure on `add_circle`, see
`add_circle.normed_add_comm_group` in a later file.
See also `Circle` and `Real.angle`. For the normed group structure on `AddCircle`, see
`AddCircle.NormedAddCommGroup` in a later file.
## Main definitions and results:
* `add_circle`: the additive circle `π•œ β§Έ (β„€ βˆ™ p)` for some period `p : π•œ`
* `unit_add_circle`: the special case `ℝ β§Έ β„€`
* `add_circle.equiv_add_circle`: the rescaling equivalence `add_circle p ≃+ add_circle q`
* `add_circle.equiv_Ico`: the natural equivalence `add_circle p ≃ Ico a (a + p)`
* `add_circle.add_order_of_div_of_gcd_eq_one`: rational points have finite order
* `add_circle.exists_gcd_eq_one_of_is_of_fin_add_order`: finite-order points are rational
* `add_circle.homeo_Icc_quot`: the natural topological equivalence between `add_circle p` and
* `AddCircle`: the additive circle `π•œ β§Έ (β„€ βˆ™ p)` for some period `p : π•œ`
* `UnitAddCircle`: the special case `ℝ β§Έ β„€`
* `AddCircle.equivAddCircle`: the rescaling equivalence `AddCircle p ≃+ AddCircle q`
* `AddCircle.equivIco`: the natural equivalence `AddCircle p ≃ Ico a (a + p)`
* `AddCircle.addOrderOf_div_of_gcd_eq_one`: rational points have finite order
* `AddCircle.exists_gcd_eq_one_of_isOfFinAddOrder`: finite-order points are rational
* `AddCircle.homeoIccQuot`: the natural topological equivalence between `AddCircle p` and
`Icc a (a + p)` with its endpoints identified.
* `add_circle.lift_Ico_continuous`: if `f : ℝ β†’ B` is continuous, and `f a = f (a + p)` for
some `a`, then there is a continuous function `add_circle p β†’ B` which agrees with `f` on
* `AddCircle.liftIco_continuous`: if `f : ℝ β†’ B` is continuous, and `f a = f (a + p)` for
some `a`, then there is a continuous function `AddCircle p β†’ B` which agrees with `f` on
`Icc a (a + p)`.
## Implementation notes:
Although the most important case is `π•œ = ℝ` we wish to support other types of scalars, such as
the rational circle `add_circle (1 : β„š)`, and so we set things up more generally.
the rational circle `AddCircle (1 : β„š)`, and so we set things up more generally.
## TODO
* Link with periodicity
* Lie group structure
* Exponential equivalence to `circle`
* Exponential equivalence to `Circle`
-/

Expand Down Expand Up @@ -121,7 +121,7 @@ theorem continuousAt_toIocMod : ContinuousAt (toIocMod hp a) x :=

end Continuity

/-- The "additive circle": `π•œ β§Έ (β„€ βˆ™ p)`. See also `circle` and `real.angle`. -/
/-- The "additive circle": `π•œ β§Έ (β„€ βˆ™ p)`. See also `Circle` and `Real.angle`. -/
@[nolint unusedArguments]
def AddCircle [LinearOrderedAddCommGroup π•œ] [TopologicalSpace π•œ] [OrderTopology π•œ] (p : π•œ) :=
π•œ β§Έ zmultiples p
Expand Down Expand Up @@ -209,25 +209,25 @@ variable [hp : Fact (0 < p)] (a : π•œ) [Archimedean π•œ]
instance : CircularOrder (AddCircle p) :=
QuotientAddGroup.circularOrder

/-- The equivalence between `add_circle p` and the half-open interval `[a, a + p)`, whose inverse
/-- The equivalence between `AddCircle p` and the half-open interval `[a, a + p)`, whose inverse
is the natural quotient map. -/
def equivIco : AddCircle p ≃ Ico a (a + p) :=
QuotientAddGroup.equivIcoMod hp.out a
#align add_circle.equiv_Ico AddCircle.equivIco

/-- The equivalence between `add_circle p` and the half-open interval `(a, a + p]`, whose inverse
/-- The equivalence between `AddCircle p` and the half-open interval `(a, a + p]`, whose inverse
is the natural quotient map. -/
def equivIoc : AddCircle p ≃ Ioc a (a + p) :=
QuotientAddGroup.equivIocMod hp.out a
#align add_circle.equiv_Ioc AddCircle.equivIoc

/-- Given a function on `π•œ`, return the unique function on `add_circle p` agreeing with `f` on
/-- Given a function on `π•œ`, return the unique function on `AddCircle p` agreeing with `f` on
`[a, a + p)`. -/
def liftIco (f : π•œ β†’ B) : AddCircle p β†’ B :=
restrict _ f ∘ AddCircle.equivIco p a
#align add_circle.lift_Ico AddCircle.liftIco

/-- Given a function on `π•œ`, return the unique function on `add_circle p` agreeing with `f` on
/-- Given a function on `π•œ`, return the unique function on `AddCircle p` agreeing with `f` on
`(a, a + p]`. -/
def liftIoc (f : π•œ β†’ B) : AddCircle p β†’ B :=
restrict _ f ∘ AddCircle.equivIoc p a
Expand Down Expand Up @@ -292,23 +292,23 @@ theorem continuousAt_equivIoc : ContinuousAt (equivIoc p a) x := by

end Continuity

/-- The image of the closed-open interval `[a, a + p)` under the quotient map `π•œ β†’ add_circle p` is
/-- The image of the closed-open interval `[a, a + p)` under the quotient map `π•œ β†’ AddCircle p` is
the entire space. -/
@[simp]
theorem coe_image_Ico_eq : ((↑) : π•œ β†’ AddCircle p) '' Ico a (a + p) = univ := by
rw [image_eq_range]
exact (equivIco p a).symm.range_eq_univ
#align add_circle.coe_image_Ico_eq AddCircle.coe_image_Ico_eq

/-- The image of the closed-open interval `[a, a + p)` under the quotient map `π•œ β†’ add_circle p` is
/-- The image of the closed-open interval `[a, a + p)` under the quotient map `π•œ β†’ AddCircle p` is
the entire space. -/
@[simp]
theorem coe_image_Ioc_eq : ((↑) : π•œ β†’ AddCircle p) '' Ioc a (a + p) = univ := by
rw [image_eq_range]
exact (equivIoc p a).symm.range_eq_univ
#align add_circle.coe_image_Ioc_eq AddCircle.coe_image_Ioc_eq

/-- The image of the closed interval `[0, p]` under the quotient map `π•œ β†’ add_circle p` is the
/-- The image of the closed interval `[0, p]` under the quotient map `π•œ β†’ AddCircle p` is the
entire space. -/
@[simp]
theorem coe_image_Icc_eq : ((↑) : π•œ β†’ AddCircle p) '' Icc a (a + p) = univ :=
Expand Down Expand Up @@ -453,7 +453,7 @@ theorem exists_gcd_eq_one_of_isOfFinAddOrder {u : AddCircle p} (h : IsOfFinAddOr
variable (p)

/-- The natural bijection between points of order `n` and natural numbers less than and coprime to
`n`. The inverse of the map sends `m ↦ (m/n * p : add_circle p)` where `m` is coprime to `n` and
`n`. The inverse of the map sends `m ↦ (m/n * p : AddCircle p)` where `m` is coprime to `n` and
satisfies `0 ≀ m < n`. -/
def setAddOrderOfEquiv {n : β„•} (hn : 0 < n) :
{ u : AddCircle p | addOrderOf u = n } ≃ { m | m < n ∧ m.gcd n = 1 } :=
Expand Down Expand Up @@ -544,8 +544,8 @@ abbrev UnitAddCircle :=

section IdentifyIccEnds

/-! This section proves that for any `a`, the natural map from `[a, a + p] βŠ‚ π•œ` to `add_circle p`
gives an identification of `add_circle p`, as a topological space, with the quotient of `[a, a + p]`
/-! This section proves that for any `a`, the natural map from `[a, a + p] βŠ‚ π•œ` to `AddCircle p`
gives an identification of `AddCircle p`, as a topological space, with the quotient of `[a, a + p]`
by the equivalence relation identifying the endpoints. -/


Expand All @@ -565,7 +565,7 @@ inductive EndpointIdent : Icc a (a + p) β†’ Icc a (a + p) β†’ Prop

variable [Archimedean π•œ]

/-- The equivalence between `add_circle p` and the quotient of `[a, a + p]` by the relation
/-- The equivalence between `AddCircle p` and the quotient of `[a, a + p]` by the relation
identifying the endpoints. -/
def equivIccQuot : 𝕋 ≃ Quot (EndpointIdent p a) where
toFun x := Quot.mk _ <| inclusion Ico_subset_Icc_self (equivIco _ _ x)
Expand Down Expand Up @@ -631,7 +631,7 @@ def homeoIccQuot : 𝕋 β‰ƒβ‚œ Quot (EndpointIdent p a) where
#align add_circle.homeo_Icc_quot AddCircle.homeoIccQuot

/-! We now show that a continuous function on `[a, a + p]` satisfying `f a = f (a + p)` is the
pullback of a continuous function on `add_circle p`. -/
pullback of a continuous function on `AddCircle p`. -/


variable {p a}
Expand Down

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