Warn against exact floating-point comparsions. #8583
Description
What it does
Warns against usage of exact comparison operators (== and !=, not things like > or <=) since floating point numbers rarely are exactly equal.
Where I got the idea from: https://gforth.org/manual/Floating-Point-Tutorial.html
Prior art: https://users.rust-lang.org/t/comparing-floats-for-equality/54523 and https://bitbashing.io/comparing-floats.html
Lint Name
exact-floating-point
Category
pedantic
Advantage
- Avoids subtle errors
Drawbacks
There might be occasions where the programmer knows that the value is exact (e.g. inf or nan should be common – although they should be handled by dedicated functions).
Example
let a = 0.1f64;
let b = 0.2f64;
if a + b == 0.3
{
println!("This isn't reachable!");
}Could be written as:
let a = 0.1f64;
let b = 0.2;
if (a + b - 0.3).abs() < 0.001*((a+b).abs()+0.3f64.abs())
{
println!("This is reachable!");
}