theorem PreviewRuntimeShowcase.CodePanelDecls.previewExternalTheoremPreviewRuntimeShowcase.CodePanelDecls.previewExternalTheorem : True :
  TrueTrue : Prop`True` is a proposition and has only an introduction rule, `True.intro : True`.
In other words, `True` is simply true, and has a canonical proof, `True.intro`
For more information: [Propositional Logic](https://lean-lang.org/theorem_proving_in_lean4/propositions_and_proofs.html#propositional-logic)

theorem PreviewRuntimeShowcase.CodePanelDecls.previewDocstringedTheoremPreviewRuntimeShowcase.CodePanelDecls.previewDocstringedTheorem : TrueA documented preview theorem whose statement is intentionally small.
 :
  TrueTrue : Prop`True` is a proposition and has only an introduction rule, `True.intro : True`.
In other words, `True` is simply true, and has a canonical proof, `True.intro`
For more information: [Propositional Logic](https://lean-lang.org/theorem_proving_in_lean4/propositions_and_proofs.html#propositional-logic)

theorem PreviewRuntimeShowcase.CodePanelDecls.previewExternalTheoremPreviewRuntimeShowcase.CodePanelDecls.previewExternalTheorem : True :
  TrueTrue : Prop`True` is a proposition and has only an introduction rule, `True.intro : True`.
In other words, `True` is simply true, and has a canonical proof, `True.intro`
For more information: [Propositional Logic](https://lean-lang.org/theorem_proving_in_lean4/propositions_and_proofs.html#propositional-logic)

theorem PreviewRuntimeShowcase.CodePanelDecls.previewExternalTheoremTwoPreviewRuntimeShowcase.CodePanelDecls.previewExternalTheoremTwo : True :
  TrueTrue : Prop`True` is a proposition and has only an introduction rule, `True.intro : True`.
In other words, `True` is simply true, and has a canonical proof, `True.intro`
For more information: [Propositional Logic](https://lean-lang.org/theorem_proving_in_lean4/propositions_and_proofs.html#propositional-logic)

theorem PreviewRuntimeShowcase.CodePanelDecls.previewExternalSorryPreviewRuntimeShowcase.CodePanelDecls.previewExternalSorry : True :
  TrueTrue : Prop`True` is a proposition and has only an introduction rule, `True.intro : True`.
In other words, `True` is simply true, and has a canonical proof, `True.intro`
For more information: [Propositional Logic](https://lean-lang.org/theorem_proving_in_lean4/propositions_and_proofs.html#propositional-logic)

theorem PreviewRuntimeShowcase.CodePanelDecls.previewExternalTheoremPreviewRuntimeShowcase.CodePanelDecls.previewExternalTheorem : True :
  TrueTrue : Prop`True` is a proposition and has only an introduction rule, `True.intro : True`.
In other words, `True` is simply true, and has a canonical proof, `True.intro`
For more information: [Propositional Logic](https://lean-lang.org/theorem_proving_in_lean4/propositions_and_proofs.html#propositional-logic)

theorem PreviewRuntimeShowcase.CodePanelDecls.previewExternalSorryPreviewRuntimeShowcase.CodePanelDecls.previewExternalSorry : True :
  TrueTrue : Prop`True` is a proposition and has only an introduction rule, `True.intro : True`.
In other words, `True` is simply true, and has a canonical proof, `True.intro`
For more information: [Propositional Logic](https://lean-lang.org/theorem_proving_in_lean4/propositions_and_proofs.html#propositional-logic)

theorem PreviewRuntimeShowcase.CodePanelDecls.previewExternalTheoremPreviewRuntimeShowcase.CodePanelDecls.previewExternalTheorem : True :
  TrueTrue : Prop`True` is a proposition and has only an introduction rule, `True.intro : True`.
In other words, `True` is simply true, and has a canonical proof, `True.intro`
For more information: [Propositional Logic](https://lean-lang.org/theorem_proving_in_lean4/propositions_and_proofs.html#propositional-logic)

theorem Nat.add_assocNat.add_assoc (n m k : Nat) : n + m + k = n + (m + k) (nNat mNat kNat : NatNat : TypeThe natural numbers, starting at zero.

This type is special-cased by both the kernel and the compiler, and overridden with an efficient
implementation. Both use a fast arbitrary-precision arithmetic library (usually
[GMP](https://gmplib.org/)); at runtime, `Nat` values that are sufficiently small are unboxed.
) :
  nNat +HAdd.hAdd.{u, v, w} {α : Type u} {β : Type v} {γ : outParam (Type w)} [self : HAdd α β γ] : α → β → γ`a + b` computes the sum of `a` and `b`.
The meaning of this notation is type-dependent. 

Conventions for notations in identifiers:

 * The recommended spelling of `+` in identifiers is `add`. mNat +HAdd.hAdd.{u, v, w} {α : Type u} {β : Type v} {γ : outParam (Type w)} [self : HAdd α β γ] : α → β → γ`a + b` computes the sum of `a` and `b`.
The meaning of this notation is type-dependent. 

Conventions for notations in identifiers:

 * The recommended spelling of `+` in identifiers is `add`. kNat =Eq.{u_1} {α : Sort u_1} : α → α → PropThe equality relation. It has one introduction rule, `Eq.refl`.
We use `a = b` as notation for `Eq a b`.
A fundamental property of equality is that it is an equivalence relation.
```
variable (α : Type) (a b c d : α)
variable (hab : a = b) (hcb : c = b) (hcd : c = d)

example : a = d :=
  Eq.trans (Eq.trans hab (Eq.symm hcb)) hcd
```
Equality is much more than an equivalence relation, however. It has the important property that every assertion
respects the equivalence, in the sense that we can substitute equal expressions without changing the truth value.
That is, given `h1 : a = b` and `h2 : p a`, we can construct a proof for `p b` using substitution: `Eq.subst h1 h2`.
Example:
```
example (α : Type) (a b : α) (p : α → Prop)
        (h1 : a = b) (h2 : p a) : p b :=
  Eq.subst h1 h2

example (α : Type) (a b : α) (p : α → Prop)
    (h1 : a = b) (h2 : p a) : p b :=
  h1 ▸ h2
```
The triangle in the second presentation is a macro built on top of `Eq.subst` and `Eq.symm`, and you can enter it by typing `\t`.
For more information: [Equality](https://lean-lang.org/theorem_proving_in_lean4/quantifiers_and_equality.html#equality)


Conventions for notations in identifiers:

 * The recommended spelling of `=` in identifiers is `eq`. nNat +HAdd.hAdd.{u, v, w} {α : Type u} {β : Type v} {γ : outParam (Type w)} [self : HAdd α β γ] : α → β → γ`a + b` computes the sum of `a` and `b`.
The meaning of this notation is type-dependent. 

Conventions for notations in identifiers:

 * The recommended spelling of `+` in identifiers is `add`. (HAdd.hAdd.{u, v, w} {α : Type u} {β : Type v} {γ : outParam (Type w)} [self : HAdd α β γ] : α → β → γ`a + b` computes the sum of `a` and `b`.
The meaning of this notation is type-dependent. 

Conventions for notations in identifiers:

 * The recommended spelling of `+` in identifiers is `add`.mNat +HAdd.hAdd.{u, v, w} {α : Type u} {β : Type v} {γ : outParam (Type w)} [self : HAdd α β γ] : α → β → γ`a + b` computes the sum of `a` and `b`.
The meaning of this notation is type-dependent. 

Conventions for notations in identifiers:

 * The recommended spelling of `+` in identifiers is `add`. kNat)HAdd.hAdd.{u, v, w} {α : Type u} {β : Type v} {γ : outParam (Type w)} [self : HAdd α β γ] : α → β → γ`a + b` computes the sum of `a` and `b`.
The meaning of this notation is type-dependent. 

Conventions for notations in identifiers:

 * The recommended spelling of `+` in identifiers is `add`.

theorem PreviewRuntimeShowcase.CodePanelDecls.PreviewFreyPackage.ofCounterexamplePreviewRuntimeShowcase.CodePanelDecls.PreviewFreyPackage.ofCounterexample {a b c p : Nat} (hp5 : 5 ≤ p)
  (H : a ^ p + b ^ p = c ^ p) : Nonempty PreviewRuntimeShowcase.CodePanelDecls.PreviewFreyPackageGiven a counterexample `a^p + b^p = c^p` with `p >= 5`,
there exists a preview Frey package.

  {aNat bNat cNat pNat : NatNat : TypeThe natural numbers, starting at zero.

This type is special-cased by both the kernel and the compiler, and overridden with an efficient
implementation. Both use a fast arbitrary-precision arithmetic library (usually
[GMP](https://gmplib.org/)); at runtime, `Nat` values that are sufficiently small are unboxed.
} (hp55 ≤ p : 5 ≤LE.le.{u} {α : Type u} [self : LE α] : α → α → PropThe less-equal relation: `x ≤ y` 

Conventions for notations in identifiers:

 * The recommended spelling of `≤` in identifiers is `le`. pNat)
  (Ha ^ p + b ^ p = c ^ p : aNat ^HPow.hPow.{u, v, w} {α : Type u} {β : Type v} {γ : outParam (Type w)} [self : HPow α β γ] : α → β → γ`a ^ b` computes `a` to the power of `b`.
The meaning of this notation is type-dependent. 

Conventions for notations in identifiers:

 * The recommended spelling of `^` in identifiers is `pow`. pNat +HAdd.hAdd.{u, v, w} {α : Type u} {β : Type v} {γ : outParam (Type w)} [self : HAdd α β γ] : α → β → γ`a + b` computes the sum of `a` and `b`.
The meaning of this notation is type-dependent. 

Conventions for notations in identifiers:

 * The recommended spelling of `+` in identifiers is `add`. bNat ^HPow.hPow.{u, v, w} {α : Type u} {β : Type v} {γ : outParam (Type w)} [self : HPow α β γ] : α → β → γ`a ^ b` computes `a` to the power of `b`.
The meaning of this notation is type-dependent. 

Conventions for notations in identifiers:

 * The recommended spelling of `^` in identifiers is `pow`. pNat =Eq.{u_1} {α : Sort u_1} : α → α → PropThe equality relation. It has one introduction rule, `Eq.refl`.
We use `a = b` as notation for `Eq a b`.
A fundamental property of equality is that it is an equivalence relation.
```
variable (α : Type) (a b c d : α)
variable (hab : a = b) (hcb : c = b) (hcd : c = d)

example : a = d :=
  Eq.trans (Eq.trans hab (Eq.symm hcb)) hcd
```
Equality is much more than an equivalence relation, however. It has the important property that every assertion
respects the equivalence, in the sense that we can substitute equal expressions without changing the truth value.
That is, given `h1 : a = b` and `h2 : p a`, we can construct a proof for `p b` using substitution: `Eq.subst h1 h2`.
Example:
```
example (α : Type) (a b : α) (p : α → Prop)
        (h1 : a = b) (h2 : p a) : p b :=
  Eq.subst h1 h2

example (α : Type) (a b : α) (p : α → Prop)
    (h1 : a = b) (h2 : p a) : p b :=
  h1 ▸ h2
```
The triangle in the second presentation is a macro built on top of `Eq.subst` and `Eq.symm`, and you can enter it by typing `\t`.
For more information: [Equality](https://lean-lang.org/theorem_proving_in_lean4/quantifiers_and_equality.html#equality)


Conventions for notations in identifiers:

 * The recommended spelling of `=` in identifiers is `eq`. cNat ^HPow.hPow.{u, v, w} {α : Type u} {β : Type v} {γ : outParam (Type w)} [self : HPow α β γ] : α → β → γ`a ^ b` computes `a` to the power of `b`.
The meaning of this notation is type-dependent. 

Conventions for notations in identifiers:

 * The recommended spelling of `^` in identifiers is `pow`. pNat) :
  NonemptyNonempty.{u} (α : Sort u) : Prop`Nonempty α` is a typeclass that says that `α` is not an empty type,
that is, there exists an element in the type. It differs from `Inhabited α`
in that `Nonempty α` is a `Prop`, which means that it does not actually carry
an element of `α`, only a proof that *there exists* such an element.
Given `Nonempty α`, you can construct an element of `α` *nonconstructively*
using `Classical.choice`.

    PreviewRuntimeShowcase.CodePanelDecls.PreviewFreyPackagePreviewRuntimeShowcase.CodePanelDecls.PreviewFreyPackage : TypeA preview Frey package is a compact stand-in for a structure whose constructor
duplicates a field-heavy mathematical record.

theorem PreviewRuntimeShowcase.CodePanelDecls.previewDocstringedTheoremPreviewRuntimeShowcase.CodePanelDecls.previewDocstringedTheorem : TrueA documented preview theorem whose statement is intentionally small.
 :
  TrueTrue : Prop`True` is a proposition and has only an introduction rule, `True.intro : True`.
In other words, `True` is simply true, and has a canonical proof, `True.intro`
For more information: [Propositional Logic](https://lean-lang.org/theorem_proving_in_lean4/propositions_and_proofs.html#propositional-logic)