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[Merged by Bors] - fix(data/{Finset,Multiset}): better line breaks in Repr #6333

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[Merged by Bors] - fix(data/{Finset,Multiset}): better line breaks in Repr #6333

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6 changes: 4 additions & 2 deletions Mathlib/Data/Finset/Sort.lean
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Expand Up @@ -253,7 +253,9 @@ theorem orderEmbOfCardLe_mem (s : Finset α) {k : ℕ} (h : k ≤ s.card) (a) :

end SortLinearOrder

unsafe instance [Repr α] : Repr (Finset α) :=
⟨fun s _ => repr s.1⟩
unsafe instance [Repr α] : Repr (Finset α) where
reprPrec s _ :=
-- multiset uses `0` not `∅` for empty sets
if s.card = 0 then "∅" else repr s.1

end Finset
8 changes: 6 additions & 2 deletions Mathlib/Data/Multiset/Sort.lean
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Expand Up @@ -68,7 +68,11 @@ theorem sort_singleton (a : α) : sort r {a} = [a] :=
end sort

-- TODO: use a sort order if available, gh-18166
unsafe instance [Repr α] : Repr (Multiset α) :=
⟨fun s _ => "{" ++ Std.Format.joinSep (s.unquot.map repr) ", " ++ "}"⟩
unsafe instance [Repr α] : Repr (Multiset α) where
reprPrec s _ :=
if Multiset.card s = 0 then
"0"
else
Std.Format.bracket "{" (Std.Format.joinSep (s.unquot.map repr) ("," ++ Std.Format.line)) "}"

end Multiset
11 changes: 11 additions & 0 deletions test/finset_repr.lean
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@@ -0,0 +1,11 @@
import Mathlib.Data.Finset.Sort

#eval show Lean.MetaM Unit from guard <|
(repr (0 : Multiset (List ℕ)) |>.pretty 15) = "0"
Comment on lines +3 to +4
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These tests might be clearer with a simple #guard_msgs, rather than mentioning MetaM.

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I specifically want to use a narrow width, so would prefer to test equality.

Is there a better way to write simple assertions than what I do here?

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There are a handful of other tests in this style, so I'm going to leave it as is for now

bors merge

#eval show Lean.MetaM Unit from guard <|
(repr ({[1, 2, 3], [4, 5, 6]} : Multiset (List ℕ)) |>.pretty 15) = "{[1, 2, 3],\n [4, 5, 6]}"

#eval show Lean.MetaM Unit from guard <|
(repr (∅ : Finset (List ℕ)) |>.pretty 15) = "∅"
#eval show Lean.MetaM Unit from guard <|
(repr ({[1, 2, 3], [4, 5, 6]} : Finset (List ℕ)) |>.pretty 15) = "{[1, 2, 3],\n [4, 5, 6]}"