09a5b34931
This PR adjusts the experimental module system to make `private` the default visibility modifier in `module`s, introducing `public` as a new modifier instead. `public section` can be used to revert the default for an entire section, though this is more intended to ease gradual adoption of the new semantics such as in `Init` (and soon `Std`) where they should be replaced by a future decl-by-decl re-review of visibilities.
81 lines
3.6 KiB
Text
81 lines
3.6 KiB
Text
/-
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Copyright (c) 2022 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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Author: Leonardo de Moura
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-/
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module
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prelude
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public import Init.SizeOf
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public import Init.MetaTypes
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public import Init.WF
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public section
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/--
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Unfold definitions commonly used in well founded relation definitions.
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Since Lean 4.12, Lean unfolds these definitions automatically before presenting the goal to the
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user, and this tactic should no longer be necessary. Calls to `simp_wf` can be removed or replaced
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by plain calls to `simp`.
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-/
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macro "simp_wf" : tactic =>
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`(tactic| try simp +unfoldPartialApp +zetaDelta [invImage, InvImage, Prod.lex, sizeOfWFRel, measure, Nat.lt_wfRel, WellFoundedRelation.rel])
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/--
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This tactic is used internally by lean before presenting the proof obligations from a well-founded
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definition to the user via `decreasing_by`. It is not necessary to use this tactic manually.
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-/
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macro "clean_wf" : tactic =>
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`(tactic| simp +unfoldPartialApp +zetaDelta -failIfUnchanged
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only [invImage, InvImage, Prod.lex, sizeOfWFRel, measure, Nat.lt_wfRel,
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WellFoundedRelation.rel, sizeOf_nat, reduceCtorEq])
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/-- Extensible helper tactic for `decreasing_tactic`. This handles the "base case"
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reasoning after applying lexicographic order lemmas.
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It can be extended by adding more macro definitions, e.g.
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```
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macro_rules | `(tactic| decreasing_trivial) => `(tactic| linarith)
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```
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-/
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syntax "decreasing_trivial" : tactic
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macro_rules | `(tactic| decreasing_trivial) => `(tactic| (simp +arith -failIfUnchanged) <;> done)
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macro_rules | `(tactic| decreasing_trivial) => `(tactic| omega)
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macro_rules | `(tactic| decreasing_trivial) => `(tactic| assumption)
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/--
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Variant of `decreasing_trivial` that does not use `omega`, intended to be used in core modules
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before `omega` is available.
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-/
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syntax "decreasing_trivial_pre_omega" : tactic
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macro_rules | `(tactic| decreasing_trivial_pre_omega) => `(tactic| apply Nat.sub_succ_lt_self; assumption) -- a - (i+1) < a - i if i < a
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macro_rules | `(tactic| decreasing_trivial_pre_omega) => `(tactic| apply Nat.pred_lt_of_lt; assumption) -- i-1 < i if j < i
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macro_rules | `(tactic| decreasing_trivial_pre_omega) => `(tactic| apply Nat.pred_lt; assumption) -- i-1 < i if i ≠ 0
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/-- Constructs a proof of decreasing along a well founded relation, by simplifying, then applying
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lexicographic order lemmas and finally using `ts` to solve the base case. If it fails,
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it prints a message to help the user diagnose an ill-founded recursive definition. -/
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macro "decreasing_with " ts:tacticSeq : tactic =>
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`(tactic|
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(clean_wf -- remove after next stage0 update
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try simp
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repeat (first | apply Prod.Lex.right | apply Prod.Lex.left)
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repeat (first | apply PSigma.Lex.right | apply PSigma.Lex.left)
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first
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| done
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| $ts
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| fail "failed to prove termination, possible solutions:
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- Use `have`-expressions to prove the remaining goals
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- Use `termination_by` to specify a different well-founded relation
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- Use `decreasing_by` to specify your own tactic for discharging this kind of goal"))
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/-- `decreasing_tactic` is called by default on well-founded recursions in order
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to synthesize a proof that recursive calls decrease along the selected
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well founded relation. It can be locally overridden by using `decreasing_by tac`
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on the recursive definition, and it can also be globally extended by adding
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more definitions for `decreasing_tactic` (or `decreasing_trivial`,
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which this tactic calls). -/
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macro "decreasing_tactic" : tactic =>
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`(tactic| decreasing_with first | decreasing_trivial | subst_vars; decreasing_trivial)
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