Prevents using `==` and `!=` operators on floats and doubles

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Metadata

ID: csharp-best-practices/float-equality

Language: C#

Severity: Error

Category: Best Practices

Description

Floating point math is inherently imprecise, so checking strict equality to a float or double will very likely lead to unexpected bugs.

For example: Input

var a = 0.1f;
var b = 0.2f;
var c = 0.3f;
Console.WriteLine($"{a + b == c}");

Output

False

(Note: exact results can vary depending on the compiler used)

Non-Compliant Code Examples

class NonCompliant
{
    public static void Main()
    {
        float foo = 1.2345f;

        if (foo == 1.2345f) { /* ... */ }

        if (4.567d == 4.567d) { /* ... */ }
        if (4.567f != 4.567f) { /* ... */ }

        bool isEqual = foo == 1.2345f;
    }
}

Compliant Code Examples

class Compliant
{
    public static void Main()
    {
        float foo = 1.2345f;
        var tolerance = 0.000000001f;
        if (Math.Abs(foo - 1.2345f) < tolerance) { /* ... */ }
    }
}

How to use this rule

1
2
rulesets:
  - csharp-best-practices     # Rules to enforce C# best practices.

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