Crate is_close[−][src]

Expand description

Determine whether floating point numbers are close in value

In use cases such as 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. There are a few paramenters playing into the comparison of two floats. is_close comes with sane default settings. However, the 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. TODO 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

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(9.0, 10.0));
assert!(!ic(10.0, 9.0));

Macros

all_close	Check whether or not two iterables `a` and `b` are pairwise close to each other
any_close	Check whether or not two iterables `a` and `b` are pairwise close to each other in at least one place
is_close	Check whether or not two values `a` and `b` are close to each other

ASYMMETRIC	Shorthand for `Method::Asymmetric`
AVERAGE	Shorthand for `Method::Average`
STRONG	Shorthand for `Method::Strong`
WEAK	Shorthand for `Method::Weak`

Functions

default

Create default IsClose configuration: { rel_tol: 1e-8, abs_tol: 0.0, method: "weak" }