numeric_statistics/f32/
max.rs

1/// Calculate statistical max for values.
2///
3/// # Nan
4/// 
5/// Return NaN if the values are empty.
6///
7/// From <https://doc.rust-lang.org/std/primitive.f32.html#method.max>:
8///
9/// If one of the arguments is NaN, then the other argument is returned. This
10/// follows the IEEE 754-2008 semantics for maxNum, except for handling of
11/// signaling NaNs; this function handles all NaNs the same way and avoids
12/// maxNum’s problems with associativity. This also matches the behavior of
13/// libm’s fmax. In particular, if the inputs compare equal (such as for the case
14/// of +0.0 and -0.0), either input may be returned non-deterministically.
15///
16/// # Example
17///
18/// ```rust
19/// use numeric_statistics::f64::max::*;
20/// let values = &[1.0, 2.0, 4.0];
21/// let max = max(values);
22/// assert_eq!(max, 4.0);
23/// ```
24/// 
25pub fn max<T: AsRef<[f32]>>(values: T) -> f32 {
26    let values = values.as_ref();
27    if values.is_empty() { return f32::NAN; }
28    values.iter().fold(f32::NAN, |a, x| f32::max(a, *x))
29}
30
31#[cfg(test)]
32mod test {
33    use super::*;
34
35    #[test]
36    fn test_empty() {
37        let x: &[f32] = &[];
38        assert!(max(x).is_nan());
39    }
40
41    #[test]
42    fn test_nan() {
43        let x: &[f32] = &[f32::NAN];
44        assert!(max(x).is_nan());
45    }
46
47    #[test]
48    fn test_value() {
49        let x: &[f32] = &[1.0];
50        assert_eq!(max(x), 1.0);
51    }
52
53    #[test]
54    fn test_values_ascending() {
55        let x = &[1.0, 2.0, 3.0];
56        assert_eq!(max(x), 3.0);
57    }
58
59    #[test]
60    fn test_values_ascending_and_nans() {
61        let x = &[1.0, f32::NAN, 2.0, f32::NAN, 3.0];
62        assert_eq!(max(x), 3.0);
63    }
64
65    #[test]
66    fn test_values_descending() {
67        let x = &[3.0, 2.0, 1.0];
68        assert_eq!(max(x), 3.0);
69    }
70
71    #[test]
72    fn test_values_descending_and_nans() {
73        let x = &[3.0, f32::NAN, 2.0, f32::NAN, 1.0];
74        assert_eq!(max(x), 3.0);
75    }
76
77}
numeric_statistics/f32/max.rs

numeric_statistics/f32/
max.rs
