Replace π-related bound constants with next_up/next_down #16823
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- Replaced 8 hardcoded π constants with std library next_up/next_down methods - All f32 constants remain identical (perfect precision match) - f64 π constants improved by ~4.4e-16 (better mathematical precision) - Removed clippy::approx_constant allows (no longer needed) - Updated comments to explain bounds purpose and method - Removed obsolete TODO comment about next_up/next_down stabilization Closes apache#16712"
alamb
approved these changes
Jul 19, 2025
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Thanks @rthummaluru -- once this this PR passes CI tests it looks good to me
findepi
approved these changes
Jul 22, 2025
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Current MSRV is 1.85.1. We need to wait until MSRV=1.86. |
alamb
added
the
waiting-on-upstream
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MSRV was updated by @adriangb in I merged up from main and kicked off tests again |
adriangb
approved these changes
Aug 22, 2025
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I think this one is good to go -- it has been waiting until we could use the new rust features |
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Thanks everyone |
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Which issue does this PR close?
Closes #16712.
Rationale for this change
Rust 1.86 stabilized f64::next_up() and f32::next_up() methods, along with their next_down() counterparts. These methods provide IEEE 754 compliant ways to get the next representable floating-point value, which is more precise and maintainable than manually calculated hardcoded constants.
The existing hardcoded π-related constants were close approximations, but using the standard library methods ensures mathematical correctness and improves code clarity.
What changes are included in this PR?
Replaced 8 hardcoded π-related floating-point constants with next_up()/next_down() calls
Removed #[allow(clippy::approx_constant)] attributes (no longer needed)
Updated comments to explain the purpose (bounds) and method (next_up/next_down)
Removed obsolete TODO comment about next_up/next_down stabilization
Constants updated:
PI_UPPER_F32/F64 → std::f32/f64::consts::PI.next_up()
NEGATIVE_PI_LOWER_F32/F64 → (-std::f32/f64::consts::PI).next_down()
FRAC_PI_2_UPPER_F32/F64 → std::f32/f64::consts::FRAC_PI_2.next_up()
NEGATIVE_FRAC_PI_2_LOWER_F32/F64 → (-std::f32/f64::consts::FRAC_PI_2).next_down()
Value Analysis:
All f32 constants remain identical (perfect precision match)
f64 π constants show minor precision improvements (~4.4e-16)
f64 π/2 constants remain identical
Are these changes tested?
Yes, these changes are tested by existing tests. The constants are used in mathematical functions throughout DataFusion, and all existing tests continue to pass, confirming compatibility.