euclid/
num.rs

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1// Copyright 2014 The Servo Project Developers. See the COPYRIGHT
2// file at the top-level directory of this distribution.
3//
4// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
5// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
6// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
7// option. This file may not be copied, modified, or distributed
8// except according to those terms.
9//! A one-dimensional length, tagged with its units.
10
11use num_traits;
12
13// Euclid has its own Zero and One traits instead of of using the num_traits equivalents.
14// Unfortunately, num_traits::Zero requires Add, which opens a bag of sad things:
15//  - Most importantly, for Point2D to implement Zero it would need to implement Add<Self> which we
16//    don't want (we allow "Point + Vector" and "Vector + Vector" semantics and purposefully disallow
17//    "Point + Point".
18//  - Some operations that require, say, One and Div (for example Scale::inv) currently return a
19//    type parameterized over T::Output which is ambiguous with num_traits::One because it inherits
20//    Mul which also has an Output associated type. To fix it need to complicate type signatures
21//    by using <T as Trait>::Output which makes the code and documentation harder to read.
22//
23// On the other hand, euclid::num::Zero/One are automatically implemented for all types that
24// implement their num_traits counterpart. Euclid users never need to explicitly use
25// euclid::num::Zero/One and can/should only manipulate the num_traits equivalents without risk
26// of compatibility issues with euclid.
27
28pub trait Zero {
29    fn zero() -> Self;
30}
31
32impl<T: num_traits::Zero> Zero for T {
33    fn zero() -> T {
34        num_traits::Zero::zero()
35    }
36}
37
38pub trait One {
39    fn one() -> Self;
40}
41
42impl<T: num_traits::One> One for T {
43    fn one() -> T {
44        num_traits::One::one()
45    }
46}
47
48/// Defines the nearest integer value to the original value.
49pub trait Round: Copy {
50    /// Rounds to the nearest integer value.
51    ///
52    /// This behavior is preserved for negative values (unlike the basic cast).
53    #[must_use]
54    fn round(self) -> Self;
55}
56/// Defines the biggest integer equal or lower than the original value.
57pub trait Floor: Copy {
58    /// Rounds to the biggest integer equal or lower than the original value.
59    ///
60    /// This behavior is preserved for negative values (unlike the basic cast).
61    #[must_use]
62    fn floor(self) -> Self;
63}
64/// Defines the smallest integer equal or greater than the original value.
65pub trait Ceil: Copy {
66    /// Rounds to the smallest integer equal or greater than the original value.
67    ///
68    /// This behavior is preserved for negative values (unlike the basic cast).
69    #[must_use]
70    fn ceil(self) -> Self;
71}
72
73macro_rules! num_int {
74    ($ty:ty) => {
75        impl Round for $ty {
76            #[inline]
77            fn round(self) -> $ty {
78                self
79            }
80        }
81        impl Floor for $ty {
82            #[inline]
83            fn floor(self) -> $ty {
84                self
85            }
86        }
87        impl Ceil for $ty {
88            #[inline]
89            fn ceil(self) -> $ty {
90                self
91            }
92        }
93    };
94}
95
96macro_rules! num_float {
97    ($ty:ty) => {
98        impl Round for $ty {
99            #[inline]
100            fn round(self) -> $ty {
101                (self + 0.5).floor()
102            }
103        }
104        impl Floor for $ty {
105            #[inline]
106            fn floor(self) -> $ty {
107                num_traits::Float::floor(self)
108            }
109        }
110        impl Ceil for $ty {
111            #[inline]
112            fn ceil(self) -> $ty {
113                num_traits::Float::ceil(self)
114            }
115        }
116    };
117}
118
119num_int!(i16);
120num_int!(u16);
121num_int!(i32);
122num_int!(u32);
123num_int!(i64);
124num_int!(u64);
125num_int!(isize);
126num_int!(usize);
127num_float!(f32);
128num_float!(f64);
euclid/num.rs

euclid/
num.rs
