lean4-htt/src/Lean/Eval.lean
Leonardo de Moura b23e59d509 feat: allow #eval to update Environment
See new `MetaHasEval`.

cc @Kha
2020-07-30 16:48:31 -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, Sebastian Ullrich
-/
import Lean.Environment
namespace Lean
universe u
/-- `HasEval` extension that gives access to the current environment & options.
The basic `HasEval` class is in the prelude and should not depend on these
types. -/
class MetaHasEval (α : Type u) :=
(eval : Environment → Options → α → forall (hideUnit : optParam Bool true), IO Environment)
instance metaHasEvalOfHasEval {α : Type u} [HasEval α] : MetaHasEval α :=
⟨fun env opts a hideUnit => do HasEval.eval a hideUnit; pure env⟩
abbrev MetaIO := ReaderT (Environment × Options) IO
def MetaIO.getEnv : MetaIO Environment := do
ctx ← read; pure ctx.1
def MetaIO.getOptions : MetaIO Options := do
ctx ← read; pure ctx.2
instance MetaIO.metaHasEval {α} [MetaHasEval α] : MetaHasEval (MetaIO α) :=
⟨fun env opts x _ => do
a ← x (env, opts);
MetaHasEval.eval env opts a⟩
instance MetaIO.monadIO : MonadIO MetaIO := {}
end Lean