1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30

use std::fmt::Debug;
use std::ops::Sub;

/// Asserts if a floating point is within some epsilon.  This allows
/// you to compare calculations to make sure it's within some error factor
/// of accuracy.
///
/// This one should pass
/// ```
/// use extra_asserts::assert_approx_eq;
/// let x : f64 = 10.123456789;
/// let y : f64 = 10.123467890;
/// assert_approx_eq(x, y, &1e-4);
/// ```
///
/// This one should fail
/// ```should_panic
/// use extra_asserts::assert_approx_eq;
/// let x : f64 = 10.123456789;
/// let y : f64 = 10.123467890;
/// assert_approx_eq(x, y, &1e-10);
/// ```
pub fn assert_approx_eq<T>(l: T, r: T, epsilon: &T::Output)
where
    T: Sub + PartialOrd + Debug + Copy,
    T::Output: Debug + PartialOrd,
{
    let diff = if l < r { r - l } else { l - r };
    assert!(diff < *epsilon, format!("{:?} != {:?}", l, r));
}