61186629d6
This PR implements the option `revert`, which is set to `false` by default. To recover the old `grind` behavior, you should use `grind +revert`. Previously, `grind` used the `RevSimpIntro` idiom, i.e., it would revert all hypotheses and then re-introduce them while simplifying and applying eager `cases`. This idiom created several problems: * Users reported that `grind` would include unnecessary parameters. See [here](https://leanprover.zulipchat.com/#narrow/channel/270676-lean4/topic/Grind.20aggressively.20includes.20local.20hypotheses.2E/near/554887715). * Unnecessary section variables were also being introduced. See the new test contributed by Sebastian Graf. * Finally, it prevented us from supporting arbitrary parameters as we do in `simp`. In `simp`, I implemented a mechanism that simulates local universe-polymorphic theorems, but this approach could not be used in `grind` because there is no mechanism for reverting (and re-introducing) local universe-polymorphic theorems. Adding such a mechanism would require substantial work: I would need to modify the local context object. I considered maintaining a substitution from the original variables to the new ones, but this is also tricky, because the mapping would have to be stored in the `grind` goal objects, and it is not just a simple mapping. After reverting everything, I would need to keep a sequence of original variables that must be added to the mapping as we re-introduce them, but eager case splits complicate this quite a bit. The whole approach felt overly messy. The new behavior `grind -revert` addresses all these issues. None of the `grind` proofs in our test suite broke after we fixed the bugs exposed by the new feature. That said, the traces and counterexamples produced by `grind` are different. The new proof terms are also different.
39 lines
839 B
Text
39 lines
839 B
Text
module
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set_option grind.debug true
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open Int.Linear
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example (a b c d e : Int) :
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2*a + b ≥ 1 → b ≥ 0 → c ≥ 0 → d ≥ 0 → e ≥ 0
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→ a ≥ 3*c → c ≥ 6*e → d - e*5 ≥ 0
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→ a + b + 3*c + d + 2*e ≥ 0 := by
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grind
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set_option trace.grind.lia.model true
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/--
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trace: [grind.lia.model] a := 7
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[grind.lia.model] b := 0
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[grind.lia.model] c := 3
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[grind.lia.model] d := 2
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[grind.lia.model] e := 4
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-/
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#guard_msgs (trace) in
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example (a b c d e : Int) :
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a + b ≥ 0 →
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a = 2*c + 1 →
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c*2 = 3*d →
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c + d ≤ 0 := by
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(fail_if_success grind); sorry
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/--
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trace: [grind.lia.model] a := 17
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[grind.lia.model] b := -9
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[grind.lia.model] c := -9
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-/
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#guard_msgs (trace) in
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example (a b c : Int) :
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2*a + 3*b = 7 →
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4*a + 7*c = 5 →
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a ≥ 10 →
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False := by
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(fail_if_success grind); sorry
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