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Posted to github@arrow.apache.org by "westonpace (via GitHub)" <gi...@apache.org> on 2023/02/01 22:06:28 UTC
[GitHub] [arrow] westonpace opened a new issue, #33990: [C++] I know NAN != NAN but shouldn't literal(NAN) == literal(NAN)?
westonpace opened a new issue, #33990:
URL: https://github.com/apache/arrow/issues/33990
### Describe the usage question you have. Please include as many useful details as possible.
I'm pretty sure of this but wanted a sanity test. Also, should `literal(quiet_NAN) == literal(signaling_NAN)`? My intuition is "no".
Or...more concretely...should these test cases pass?
```
// This currently fails
EXPECT_EQ(literal(std::numeric_limits<double>::quiet_NaN()),
literal(std::numeric_limits<double>::quiet_NaN()));
// These currently pass
EXPECT_NE(literal(std::numeric_limits<double>::quiet_NaN()),
literal(std::numeric_limits<double>::signaling_NaN()));
EXPECT_NE(literal(std::numeric_limits<double>::quiet_NaN()),
literal(std::numeric_limits<float>::quiet_NaN()));
```
If the answer is "yes, those two expressions are equivalent" then I can fix it in #15180 . I already have a fix but wanted to confirm my understanding.
### Component(s)
C++
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[GitHub] [arrow] bkietz commented on issue #33990: [C++] I know NAN != NAN but shouldn't literal(NAN) == literal(NAN)?
Posted by "bkietz (via GitHub)" <gi...@apache.org>.
bkietz commented on issue #33990:
URL: https://github.com/apache/arrow/issues/33990#issuecomment-1412842913
I think that we don't need to support signalling nans. Quiet nans may be produced by floating point expressions with invalid arguments, but signalling nans can only be produced explicitly- which is not functionality I think we'd find valuable. For our purposes, I don't think we need to check for signalling nans.
I do think that `literal(nan) == literal(nan)` should be true- as you say those two expressions are equivalent. I think just to disambiguate the situation the unit test should also assert that `equal(literal(nan), literal(nan))` evaluates to false and clarify why that difference exists with a comment
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[GitHub] [arrow] jorisvandenbossche closed issue #33990: [C++] I know NAN != NAN but shouldn't literal(NAN) == literal(NAN)?
Posted by "jorisvandenbossche (via GitHub)" <gi...@apache.org>.
jorisvandenbossche closed issue #33990: [C++] I know NAN != NAN but shouldn't literal(NAN) == literal(NAN)?
URL: https://github.com/apache/arrow/issues/33990
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[GitHub] [arrow] westonpace commented on issue #33990: [C++] I know NAN != NAN but shouldn't literal(NAN) == literal(NAN)?
Posted by "westonpace (via GitHub)" <gi...@apache.org>.
westonpace commented on issue #33990:
URL: https://github.com/apache/arrow/issues/33990#issuecomment-1412832487
Ah, I can use `issignaling` which is in `<cmath>` but has no c++ equivalent.
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[GitHub] [arrow] westonpace commented on issue #33990: [C++] I know NAN != NAN but shouldn't literal(NAN) == literal(NAN)?
Posted by "westonpace (via GitHub)" <gi...@apache.org>.
westonpace commented on issue #33990:
URL: https://github.com/apache/arrow/issues/33990#issuecomment-1412824709
Actually, I can't find a good way to test if a NaN is a quiet nan or a signalling NaN so now I'm tempted to say literal(quiet_NaN) == literal(signal_NaN) as well.
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[GitHub] [arrow] jorisvandenbossche commented on issue #33990: [C++] I know NAN != NAN but shouldn't literal(NAN) == literal(NAN)?
Posted by "jorisvandenbossche (via GitHub)" <gi...@apache.org>.
jorisvandenbossche commented on issue #33990:
URL: https://github.com/apache/arrow/issues/33990#issuecomment-1433075908
This was closed by https://github.com/apache/arrow/pull/15180
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