jorisvandenbossche commented on a change in pull request #8294:
URL: https://github.com/apache/arrow/pull/8294#discussion_r504419732
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File path: cpp/src/arrow/compute/api_aggregate.h
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@@ -142,6 +142,20 @@ Result<Datum> MinMax(const Datum& value,
const MinMaxOptions& options = MinMaxOptions::Defaults(),
ExecContext* ctx = NULLPTR);
+/// \brief Test whether any element in a boolean array evaluates to true.
+///
+/// This function returns true if any of the elements in the array evaluates
+/// to true and false otherwise. Null values are taken to evaluate to false.
Review comment:
> Sorry yes. The examples were for all. Just to make sure I understand,
with kleene logic, we emit null if there's a null anywhere in the input
No, we only emit null if the presence of the null (the fact that it could be
either True or False) would influence the result:
```
any_kleene([true, null]) = true
any_kleene([false, null]) = null
all_kleene([true, null]) = null
all_kleene([false, null]) = false
```
But, the above is only when *not* skipping nulls (because with the default
of skipping, there is no difference with non-kleene logic)
See the links I mentioned in
https://github.com/apache/arrow/pull/8294#issuecomment-701357437, and also the
Julia docs have a good explanation of three-valued (Kleene) logic:
https://docs.julialang.org/en/v1/manual/missing/index.html#Logical-operators-1
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