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import Mathlib.Lean.Expr.Basic
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import NNG.MyNat.Addition
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import Lean.Elab.Tactic.Basic
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/-!
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# Modified `rw`
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Modify `rw` to work like `rewrite`.
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This is mainly a copy of the implementation of `rewrite` in Lean core.
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-/
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namespace MyNat
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open Lean.Meta Lean.Elab.Tactic Lean.Parser.Tactic
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/--
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Modified `rw` tactic. For this game, `rw` works exactly like `rewrite`.
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-/
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syntax (name := rewriteSeq) "rw" (config)? rwRuleSeq (location)? : tactic
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@[tactic MyNat.rewriteSeq] def evalRewriteSeq : Tactic := fun stx => do
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let cfg ← elabRewriteConfig stx[1]
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let loc := expandOptLocation stx[3]
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withRWRulesSeq stx[0] stx[2] fun symm term => do
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withLocation loc
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(rewriteLocalDecl term symm · cfg)
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(rewriteTarget term symm cfg)
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(throwTacticEx `rewrite · "did not find instance of the pattern in the current goal")
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/-!
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# Modified `induction` tactic
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Modify `induction` tactic to always show `(0 : MyNat)` instead of `MyNat.zero` and
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to support the lean3-style `with` keyword.
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This is mainly copied and modified from the mathlib-tactic `induction'`.
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-/
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def rec' {P : ℕ → Prop} (zero : P 0)
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(succ : (n : ℕ) → (n_ih : P n) → P (succ n)) (t : ℕ) : P t := by
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induction t with
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| zero => assumption
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| succ n =>
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apply succ
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assumption
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end MyNat
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namespace Lean.Parser.Tactic
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open Meta Elab Elab.Tactic
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open private getAltNumFields in evalCases ElimApp.evalAlts.go in
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def ElimApp.evalNames (elimInfo : ElimInfo) (alts : Array ElimApp.Alt) (withArg : Syntax)
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(numEqs := 0) (numGeneralized := 0) (toClear : Array FVarId := #[]) :
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TermElabM (Array MVarId) := do
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let mut names : List Syntax := withArg[1].getArgs |>.toList
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let mut subgoals := #[]
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for { name := altName, mvarId := g, .. } in alts do
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let numFields ← getAltNumFields elimInfo altName
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let (altVarNames, names') := names.splitAtD numFields (Unhygienic.run `(_))
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names := names'
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let (fvars, g) ← g.introN numFields <| altVarNames.map (getNameOfIdent' ·[0])
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let some (g, subst) ← Cases.unifyEqs? numEqs g {} | pure ()
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let (_, g) ← g.introNP numGeneralized
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let g ← liftM $ toClear.foldlM (·.tryClear) g
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for fvar in fvars, stx in altVarNames do
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g.withContext <| (subst.apply <| .fvar fvar).addLocalVarInfoForBinderIdent ⟨stx⟩
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subgoals := subgoals.push g
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pure subgoals
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open private getElimNameInfo generalizeTargets generalizeVars in evalInduction in
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/--
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Modified `induction` tactic for this game.
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Usage: `induction n with d hd`.
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*(The actual `induction` tactic has a more complex `with`-argument that works differently)*
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-/
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elab (name := _root_.MyNat.induction) "induction " tgts:(casesTarget,+)
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withArg:((" with " (colGt binderIdent)+)?)
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: tactic => do
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let targets ← elabCasesTargets tgts.1.getSepArgs
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let g :: gs ← getUnsolvedGoals | throwNoGoalsToBeSolved
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g.withContext do
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let elimInfo ← getElimInfo `MyNat.rec'
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let targets ← addImplicitTargets elimInfo targets
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evalInduction.checkTargets targets
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let targetFVarIds := targets.map (·.fvarId!)
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g.withContext do
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let forbidden ← mkGeneralizationForbiddenSet targets
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let mut s ← getFVarSetToGeneralize targets forbidden
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let (fvarIds, g) ← g.revert (← sortFVarIds s.toArray)
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let result ← withRef tgts <| ElimApp.mkElimApp elimInfo targets (← g.getTag)
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let elimArgs := result.elimApp.getAppArgs
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ElimApp.setMotiveArg g elimArgs[elimInfo.motivePos]!.mvarId! targetFVarIds
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g.assign result.elimApp
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let subgoals ← ElimApp.evalNames elimInfo result.alts withArg
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(numGeneralized := fvarIds.size) (toClear := targetFVarIds)
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setGoals <| (subgoals ++ result.others).toList ++ gs
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end Lean.Parser.Tactic
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/-! # `rfl` tactic
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Added `withReducible` to prevent `rfl` proving stuff like `n + 0 = n`.
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-/
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namespace MyNat
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open Lean Meta Elab Tactic
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-- @[match_pattern] def MyNat.rfl {α : Sort u} {a : α} : Eq a a := Eq.refl a
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/-- Modified `rfl` tactic.
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`rfl` closes goals of the form `A = A`.
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Note that teh version for this game is somewhat weaker than the real one. -/
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syntax (name := rfl) "rfl" : tactic
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@[tactic MyNat.rfl] def evalRfl : Tactic := fun _ =>
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liftMetaTactic fun mvarId => do withReducible <| mvarId.refl; pure []
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-- @[tactic MyNat.rfl] def evalRfl : Tactic := fun _ =>
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-- liftMetaTactic fun mvarId => do mvarId.refl; pure []
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-- (with_reducible rfl)
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end MyNat
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