How to compare floating point numbers

  1. Determine which comparison algorithm best suits your purposes.

  2. Determine the tolerance required based on the sources of the error in how the numbers were entered/calculated.

  3. If you need a boolean result, then use float_eq! or float_ne!. The two numbers should be the first and second operands, and then the tolerance is the value after the <=. For example, to compare two f32 numbers stored in a and b using a relative tolerance of tol scaled to the magnitude of the second operand:


#![allow(unused)]
fn main() {
float_eq!(a, b, r2nd <= tol)
}
  1. If instead you wish to assert that the two numbers are equal and panic if they are not, you can use assert_float_eq! or assert_float_ne!. The syntax is the same, and may optionally include formatted text after the comparisons as with standard Rust asserts:

#![allow(unused)]
fn main() {
assert_float_eq!(a, b, r2nd <= tol);
assert_float_eq!(a, b, r2nd <= tol, "Example context: {}", context);
}