lean4-htt/src/Lean/ToExpr.lean
2020-06-25 11:21:17 -07:00

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/-
Copyright (c) 2019 Microsoft Corporation. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Leonardo de Moura
-/
import Lean.Expr
universe u
namespace Lean
class ToExpr (α : Type u) :=
(toExpr : α → Expr)
(toTypeExpr : Expr)
export ToExpr (toExpr toTypeExpr)
instance exprToExpr : ToExpr Expr :=
{ toExpr := id,
toTypeExpr := mkConst `Expr }
instance natToExpr : ToExpr Nat :=
{ toExpr := mkNatLit,
toTypeExpr := mkConst `Nat }
instance boolToExpr : ToExpr Bool :=
{ toExpr := fun b => if b then mkConst `Bool.true else mkConst `Bool.false,
toTypeExpr := mkConst `Bool }
instance charToExpr : ToExpr Char :=
{ toExpr := fun c => mkApp (mkConst `Char.ofNat) (toExpr c.toNat),
toTypeExpr := mkConst `Char }
instance strToExpr : ToExpr String :=
{ toExpr := mkStrLit,
toTypeExpr := mkConst `String }
instance unitToExpr : ToExpr Unit :=
{ toExpr := fun _ => mkConst `Unit.unit,
toTypeExpr := mkConst `Unit }
def Name.toExprAux : Name → Expr
| Name.anonymous => mkConst `Lean.Name.anonymous
| Name.str p s _ => mkAppB (mkConst `Lean.mkNameStr) (Name.toExprAux p) (toExpr s)
| Name.num p n _ => mkAppB (mkConst `Lean.mkNameNum) (Name.toExprAux p) (toExpr n)
instance nameToExpr : ToExpr Name :=
{ toExpr := Name.toExprAux,
toTypeExpr := mkConst `Name }
instance optionToExpr {α : Type} [ToExpr α] : ToExpr (Option α) :=
let type := toTypeExpr α;
{ toExpr := fun o => match o with
| none => mkApp (mkConst `Option.none [levelZero]) type
| some a => mkApp2 (mkConst `Option.cons [levelZero]) type (toExpr a),
toTypeExpr := mkApp (mkConst `Option [levelZero]) type }
def List.toExprAux {α} [ToExpr α] (nilFn : Expr) (consFn : Expr) : List α → Expr
| [] => nilFn
| a::as => mkApp2 consFn (toExpr a) (List.toExprAux as)
instance listToExpr {α : Type} [ToExpr α] : ToExpr (List α) :=
let type := toTypeExpr α;
let nil := mkApp (mkConst `List.nil [levelZero]) type;
let cons := mkApp (mkConst `List.cons [levelZero]) type;
{ toExpr := List.toExprAux nil cons,
toTypeExpr := mkApp (mkConst `List [levelZero]) type }
instance arrayToExpr {α : Type} [ToExpr α] : ToExpr (Array α) :=
let type := toTypeExpr α;
{ toExpr := fun as => mkApp2 (mkConst `List.toArray [levelZero]) type (toExpr as.toList),
toTypeExpr := mkApp (mkConst `Array [levelZero]) type }
instance prodToExpr {α : Type} {β : Type} [ToExpr α] [ToExpr β] : ToExpr (α × β) :=
let αType := toTypeExpr α;
let βType := toTypeExpr β;
{ toExpr := fun ⟨a, b⟩ => mkApp4 (mkConst `Prod.mk [levelZero, levelZero]) αType βType (toExpr a) (toExpr b),
toTypeExpr := mkApp2 (mkConst `Prod [levelZero, levelZero]) αType βType }
end Lean