Crate is_close[−][src]

Expand description

Test floating point numbers for equality

In scenarios like testing it is often times more useful to know whether two floating point numbers are close to each other rather than exactly equal. Due to finite precision of computers we usually cannot even expect bitwise equality of two values even if underlaying math suggests it. This is where is_close comes in. The crate is strongly inspired by Python’s PEP 485 aka math.isclose.

Examples

Basic usage …

extern crate is_close;
use is_close::default;

assert!(default().is_close(42.0, 42.0));
assert!(!default().is_close(13.0, 37.0));

assert!(default().all_close(vec![9.0, 10.0], vec![9.0, 10.0]));
assert!(!default().all_close(vec![0.0, 10.0], vec![9.0, 10.0]));

assert!(default().any_close(vec![0.0, 10.0], vec![9.0, 10.0]));
assert!(!default().any_close(vec![0.0, 0.0], vec![9.0, 10.0]));

… and the same with macros

#[macro_use]
extern crate is_close;

assert!(is_close!(42.0, 42.0));
assert!(!is_close!(13.0, 37.0));

assert!(all_close!(vec![9.0, 10.0], vec![9.0, 10.0]));
assert!(!all_close!(vec![0.0, 10.0], vec![9.0, 10.0]));

assert!(any_close!(vec![0.0, 10.0], vec![9.0, 10.0]));
assert!(!any_close!(vec![0.0, 0.0], vec![9.0, 10.0]));

Advanced Usage

There are different ways to determine whether two values are close to each other or not. A few paramenters playing into the comparison of two floats. While is_close comes with sane [default settings], following examples illustrate how to tweak the comparison to suit your needs:

Relative Tolerance

The amount of error allowed, relative to the magnitude of the input values. Check out Method.

assert!(is_close!(9.9, 10.0, rel_tol=1e-2));
assert!(!is_close!(9.9, 10.0, rel_tol=1e-3));

Absolute Tolerance

The absolute tolerance is useful for comparisons near zero.

assert!(is_close!(0.0, 0.1, abs_tol=1e-1));
assert!(!is_close!(0.0, 0.1, abs_tol=1e-2));

Methods:

The strategy of how to interpret relative tolerance, see Method:

Weak (default): relative tolerance is scaled by the larger of the two values

use is_close::WEAK;

assert!(default().method("weak").rel_tol(1e-1).is_close(9.0, 10.0));
assert!(!default().method(WEAK).rel_tol(1e-2).is_close(9.0, 10.0));

Strong: relative tolerance is scaled by the smaller of the two values

use is_close::STRONG;

assert!(all_close!(vec![9.0, 10.0], vec![10.0, 9.0], rel_tol=2e-1, method="STRONG"));
assert!(!any_close!(vec![9.0, 10.0], vec![10.0, 9.0], rel_tol=1e-1, method=STRONG));

Average: relative tolerance is scaled by the average of the two values

use is_close::AVERAGE;

assert!(is_close!(9.0, 10.0, rel_tol=2e-1, method="average"));
assert!(!is_close!(9.0, 10.0, rel_tol=1e-1, method=AVERAGE));

Asymmetric: the second value (b) is used for scaling the tolerance

use is_close::ASYMMETRIC;

let ic = default().method(ASYMMETRIC).rel_tol(1e-1).compile();
assert!(ic.is_close(9.0, 10.0));
assert!(!ic.is_close(10.0, 9.0));