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Diffstat (limited to 'src/tools/clippy/src/docs/float_cmp.txt')
-rw-r--r-- | src/tools/clippy/src/docs/float_cmp.txt | 28 |
1 files changed, 28 insertions, 0 deletions
diff --git a/src/tools/clippy/src/docs/float_cmp.txt b/src/tools/clippy/src/docs/float_cmp.txt new file mode 100644 index 000000000..c19907c90 --- /dev/null +++ b/src/tools/clippy/src/docs/float_cmp.txt @@ -0,0 +1,28 @@ +### What it does +Checks for (in-)equality comparisons on floating-point +values (apart from zero), except in functions called `*eq*` (which probably +implement equality for a type involving floats). + +### Why is this bad? +Floating point calculations are usually imprecise, so +asking if two values are *exactly* equal is asking for trouble. For a good +guide on what to do, see [the floating point +guide](http://www.floating-point-gui.de/errors/comparison). + +### Example +``` +let x = 1.2331f64; +let y = 1.2332f64; + +if y == 1.23f64 { } +if y != x {} // where both are floats +``` + +Use instead: +``` +let error_margin = f64::EPSILON; // Use an epsilon for comparison +// Or, if Rust <= 1.42, use `std::f64::EPSILON` constant instead. +// let error_margin = std::f64::EPSILON; +if (y - 1.23f64).abs() < error_margin { } +if (y - x).abs() > error_margin { } +```
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