summaryrefslogtreecommitdiffstats
path: root/third_party/rust/float-cmp/src/ratio.rs
blob: 0a8654bba891341c9cdf24d1bb71aa1dd45dd0ab (plain)
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
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
// Copyright 2014-2018 Optimal Computing (NZ) Ltd.
// Licensed under the MIT license.  See LICENSE for details.

use std::cmp::PartialOrd;
use std::ops::{Sub,Div,Neg};
use num_traits::Zero;

/// ApproxEqRatio is a trait for approximate equality comparisons bounding the ratio
/// of the difference to the larger.
pub trait ApproxEqRatio : Div<Output = Self> + Sub<Output = Self> + Neg<Output = Self>
    + PartialOrd + Zero + Sized + Copy
{
    /// This method tests if `self` and `other` are nearly equal by bounding the
    /// difference between them to some number much less than the larger of the two.
    /// This bound is set as the ratio of the difference to the larger.
    fn approx_eq_ratio(&self, other: &Self, ratio: Self) -> bool {

        // Not equal if signs are not equal
        if *self < Self::zero() && *other > Self::zero() { return false; }
        if *self > Self::zero() && *other < Self::zero() { return false; }

        // Handle all zero cases
        match (*self == Self::zero(), *other == Self::zero()) {
            (true,true) => return true,
            (true,false) => return false,
            (false,true) => return false,
            _ => { }
        }

        // abs
        let (s,o) = if *self < Self::zero() {
            (-*self, -*other)
        } else {
            (*self, *other)
        };

        let (smaller,larger) = if s < o {
            (s,o)
        } else {
            (o,s)
        };
        let difference: Self = larger.sub(smaller);
        let actual_ratio: Self = difference.div(larger);
        actual_ratio < ratio
    }

    /// This method tests if `self` and `other` are not nearly equal by bounding the
    /// difference between them to some number much less than the larger of the two.
    /// This bound is set as the ratio of the difference to the larger.
    #[inline]
    fn approx_ne_ratio(&self, other: &Self, ratio: Self) -> bool {
        !self.approx_eq_ratio(other, ratio)
    }
}

impl ApproxEqRatio for f32 { }

#[test]
fn f32_approx_eq_ratio_test1() {
    let x: f32 = 0.00004_f32;
    let y: f32 = 0.00004001_f32;
    assert!(x.approx_eq_ratio(&y, 0.00025));
    assert!(y.approx_eq_ratio(&x, 0.00025));
    assert!(x.approx_ne_ratio(&y, 0.00024));
    assert!(y.approx_ne_ratio(&x, 0.00024));
}

#[test]
fn f32_approx_eq_ratio_test2() {
    let x: f32 = 0.00000000001_f32;
    let y: f32 = 0.00000000005_f32;
    assert!(x.approx_eq_ratio(&y, 0.81));
    assert!(y.approx_ne_ratio(&x, 0.79));
}

#[test]
fn f32_approx_eq_ratio_test_zero_eq_zero_returns_true() {
    let x: f32 = 0.0_f32;
    assert!(x.approx_eq_ratio(&x,0.1) == true);
}

#[test]
fn f32_approx_eq_ratio_test_zero_ne_zero_returns_false() {
    let x: f32 = 0.0_f32;
    assert!(x.approx_ne_ratio(&x,0.1) == false);
}

#[test]
fn f32_approx_eq_ratio_test_against_a_zero_is_false() {
    let x: f32 = 0.0_f32;
    let y: f32 = 0.1_f32;
    assert!(x.approx_eq_ratio(&y,0.1) == false);
    assert!(y.approx_eq_ratio(&x,0.1) == false);
}

#[test]
fn f32_approx_eq_ratio_test_negative_numbers() {
    let x: f32 = -3.0_f32;
    let y: f32 = -4.0_f32;
    // -3 and -4 should not be equal at a ratio of 0.1
    assert!(x.approx_eq_ratio(&y,0.1) == false);
}

impl ApproxEqRatio for f64 { }

#[test]
fn f64_approx_eq_ratio_test1() {
    let x: f64 = 0.000000004_f64;
    let y: f64 = 0.000000004001_f64;
    assert!(x.approx_eq_ratio(&y, 0.00025));
    assert!(y.approx_eq_ratio(&x, 0.00025));
    assert!(x.approx_ne_ratio(&y, 0.00024));
    assert!(y.approx_ne_ratio(&x, 0.00024));
}

#[test]
fn f64_approx_eq_ratio_test2() {
    let x: f64 = 0.0000000000000001_f64;
    let y: f64 = 0.0000000000000005_f64;
    assert!(x.approx_eq_ratio(&y, 0.81));
    assert!(y.approx_ne_ratio(&x, 0.79));
}

#[test]
fn f64_approx_eq_ratio_test_zero_eq_zero_returns_true() {
    let x: f64 = 0.0_f64;
    assert!(x.approx_eq_ratio(&x,0.1) == true);
}

#[test]
fn f64_approx_eq_ratio_test_zero_ne_zero_returns_false() {
    let x: f64 = 0.0_f64;
    assert!(x.approx_ne_ratio(&x,0.1) == false);
}

#[test]
fn f64_approx_eq_ratio_test_negative_numbers() {
    let x: f64 = -3.0_f64;
    let y: f64 = -4.0_f64;
    // -3 and -4 should not be equal at a ratio of 0.1
    assert!(x.approx_eq_ratio(&y,0.1) == false);
}