From 98bf99e2f8cf8b357d63a67ce67d5fc5ceef8b3c Mon Sep 17 00:00:00 2001
From: Philipp Krones <hello@philkrones.com>
Date: Fri, 9 Sep 2022 13:36:26 +0200
Subject: Merge commit 'b52fb5234cd7c11ecfae51897a6f7fa52e8777fc' into clippyup

---
 src/docs/float_cmp.txt | 28 ++++++++++++++++++++++++++++
 1 file changed, 28 insertions(+)
 create mode 100644 src/docs/float_cmp.txt

(limited to 'src/docs/float_cmp.txt')

diff --git a/src/docs/float_cmp.txt b/src/docs/float_cmp.txt
new file mode 100644
index 00000000000..c19907c903e
--- /dev/null
+++ b/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 { }
+```
\ No newline at end of file
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