93 lines
3 KiB
Text
93 lines
3 KiB
Text
/-
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Copyright (c) 2019 Microsoft Corporation. All rights reserved.
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Released under Apache 2.0 license as described in the file LICENSE.
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Authors: Leonardo de Moura
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-/
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import Lean.Expr
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universe u
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namespace Lean
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/--
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We use the `ToExpr` type class to convert values of type `α` into
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expressions that denote these values in Lean.
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Example:
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```
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toExpr true = .const ``Bool.true []
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```
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-/
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class ToExpr (α : Type u) where
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/-- Convert a value `a : α` into an expression that denotes `a` -/
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toExpr : α → Expr
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/-- Expression representing the type `α` -/
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toTypeExpr : Expr
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export ToExpr (toExpr toTypeExpr)
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instance : ToExpr Nat where
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toExpr := mkNatLit
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toTypeExpr := mkConst ``Nat
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instance : ToExpr Bool where
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toExpr := fun b => if b then mkConst ``Bool.true else mkConst ``Bool.false
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toTypeExpr := mkConst ``Bool
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instance : ToExpr Char where
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toExpr := fun c => mkApp (mkConst ``Char.ofNat) (toExpr c.toNat)
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toTypeExpr := mkConst ``Char
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instance : ToExpr String where
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toExpr := mkStrLit
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toTypeExpr := mkConst ``String
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instance : ToExpr Unit where
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toExpr := fun _ => mkConst `Unit.unit
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toTypeExpr := mkConst ``Unit
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private def Name.toExprAux : Name → Expr
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| .anonymous => mkConst ``Lean.Name.anonymous
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| .str p s ..=> mkApp2 (mkConst ``Lean.Name.str) (toExprAux p) (toExpr s)
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| .num p n ..=> mkApp2 (mkConst ``Lean.Name.num) (toExprAux p) (toExpr n)
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instance : ToExpr Name where
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toExpr := Name.toExprAux
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toTypeExpr := mkConst ``Name
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instance [ToExpr α] : ToExpr (Option α) :=
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let type := toTypeExpr α
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{ toExpr := fun o => match o with
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| none => mkApp (mkConst ``Option.none [levelZero]) type
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| some a => mkApp2 (mkConst ``Option.some [levelZero]) type (toExpr a),
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toTypeExpr := mkApp (mkConst ``Option [levelZero]) type }
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private def List.toExprAux [ToExpr α] (nilFn : Expr) (consFn : Expr) : List α → Expr
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| [] => nilFn
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| a::as => mkApp2 consFn (toExpr a) (toExprAux nilFn consFn as)
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instance [ToExpr α] : ToExpr (List α) :=
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let type := toTypeExpr α
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let nil := mkApp (mkConst ``List.nil [levelZero]) type
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let cons := mkApp (mkConst ``List.cons [levelZero]) type
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{ toExpr := List.toExprAux nil cons,
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toTypeExpr := mkApp (mkConst ``List [levelZero]) type }
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instance [ToExpr α] : ToExpr (Array α) :=
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let type := toTypeExpr α
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{ toExpr := fun as => mkApp2 (mkConst ``List.toArray [levelZero]) type (toExpr as.toList),
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toTypeExpr := mkApp (mkConst ``Array [levelZero]) type }
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instance [ToExpr α] [ToExpr β] : ToExpr (α × β) :=
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let αType := toTypeExpr α
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let βType := toTypeExpr β
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{ toExpr := fun ⟨a, b⟩ => mkApp4 (mkConst ``Prod.mk [levelZero, levelZero]) αType βType (toExpr a) (toExpr b),
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toTypeExpr := mkApp2 (mkConst ``Prod [levelZero, levelZero]) αType βType }
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def Expr.toCtorIfLit : Expr → Expr
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| .lit (.natVal v) =>
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if v == 0 then mkConst ``Nat.zero
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else mkApp (mkConst ``Nat.succ) (mkRawNatLit (v-1))
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| .lit (.strVal v) =>
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mkApp (mkConst ``String.mk) (toExpr v.toList)
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| e => e
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end Lean
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