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 
11 use 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 
28 pub trait Zero {
zero() -> Self29     fn zero() -> Self;
30 }
31 
32 impl<T: num_traits::Zero> Zero for T {
zero() -> T33     fn zero() -> T {
34         num_traits::Zero::zero()
35     }
36 }
37 
38 pub trait One {
one() -> Self39     fn one() -> Self;
40 }
41 
42 impl<T: num_traits::One> One for T {
one() -> T43     fn one() -> T {
44         num_traits::One::one()
45     }
46 }
47 
48 /// Defines the nearest integer value to the original value.
49 pub 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]
round(self) -> Self54     fn round(self) -> Self;
55 }
56 /// Defines the biggest integer equal or lower than the original value.
57 pub 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]
floor(self) -> Self62     fn floor(self) -> Self;
63 }
64 /// Defines the smallest integer equal or greater than the original value.
65 pub 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]
ceil(self) -> Self70     fn ceil(self) -> Self;
71 }
72 
73 macro_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) -> $ty {
90                 self
91             }
92         }
93     };
94 }
95 
96 macro_rules! num_float {
97     ($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 
119 num_int!(i16);
120 num_int!(u16);
121 num_int!(i32);
122 num_int!(u32);
123 num_int!(i64);
124 num_int!(u64);
125 num_int!(isize);
126 num_int!(usize);
127 num_float!(f32);
128 num_float!(f64);
129