4eea57841d
Sebastian mentioned that the use of the kernel defeq was to work around
a performance issue that was fixed since. Let's see if we can do
without.
This is also a semantic change: Ground terms (no free vars, no mvars)
are reduced at
“all” transparency even if the the transparency setting is default. This
was the case
even before 03f6b87647 switched to the
kernel defeq
checking for performance. It seems that this is rather surprising
behavior from the user
point of view. The fallout on batteries and mathlib is rather limited,
only a few
`rfl` proofs seem to have (inadvertently or not) have relied on this.
The speedcenter reports no significant regressions on core or mathlib.
48 lines
1.8 KiB
Text
48 lines
1.8 KiB
Text
-- NB: well-founded recursion, so irreducible
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def sorted_from_var [x: LE α] [DecidableRel x.le] (a: Array α) (i: Nat): Bool :=
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if h: i + 1 < a.size then
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have : i < a.size := Nat.lt_of_succ_lt h
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a[i] ≤ a[i+1] && sorted_from_var a (i + 1)
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else
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true
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termination_by a.size - i
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def check_sorted [x: LE α] [DecidableRel x.le] (a: Array α): Bool :=
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sorted_from_var a 0
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/--
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error: The rfl tactic failed. Possible reasons:
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- The goal is not a reflexive relation (neither `=` nor a relation with a @[refl] lemma).
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- The arguments of the relation are not equal.
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Try using the reflexivity lemma for your relation explicitly, e.g. `exact Eq.refl _` or
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`exact HEq.rfl` etc.
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⊢ check_sorted #[0, 3, 3, 5, 8, 10, 10, 10] = true
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-/
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#guard_msgs in
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example: check_sorted #[0, 3, 3, 5, 8, 10, 10, 10] = true := by
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rfl -- fails because `rfl` uses `.default` transparency, and `sorted_from_var` is marked as irreducible
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/--
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error: tactic 'decide' failed for proposition
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check_sorted #[0, 3, 3, 5, 8, 10, 10, 10] = true
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since its 'Decidable' instance
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instDecidableEqBool (check_sorted #[0, 3, 3, 5, 8, 10, 10, 10]) true
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did not reduce to 'isTrue' or 'isFalse'.
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After unfolding the instances 'instDecidableEqBool' and 'Bool.decEq', reduction got stuck at the 'Decidable' instance
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match check_sorted #[0, 3, 3, 5, 8, 10, 10, 10], true with
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| false, false => isTrue ⋯
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| false, true => isFalse ⋯
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| true, false => isFalse ⋯
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| true, true => isTrue ⋯
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-/
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#guard_msgs in
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example: check_sorted #[0, 3, 3, 5, 8, 10, 10, 10] := by
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decide -- fails because `decide` uses `.default` transparency, and `sorted_from_var` is marked as irreducible
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unseal sorted_from_var in
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example: check_sorted #[0, 3, 3, 5, 8, 10, 10, 10] := by
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decide -- works
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example: check_sorted #[0, 3, 3, 5, 8, 10, 10, 10] := by
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with_unfolding_all decide -- should work
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