path_traits/
scalar.rs

1//! Scalar type alias for arc-length and parameter computations.
2//!
3//! This module defines the [`Scalar`] trait, a numeric trait with additional bounds
4//! (`Debug`, `Copy`, `'static`) required for arc-length and parameter computations
5//! throughout the crate. The supertraits vary by feature configuration.
6
7#[cfg(all(feature = "num-traits", feature = "std"))]
8mod inner {
9    use num_traits::Float;
10
11    /// A scalar type suitable for arc-length, parameter, and distance computations.
12    ///
13    /// Requires `Float` from `num-traits` (with `std`) plus `Debug`, `Copy`, and `'static` bounds.
14    /// Implementations are provided automatically for any type satisfying those bounds
15    /// (e.g. `f32`, `f64`).
16    pub trait Scalar: Float + core::fmt::Debug + Copy + 'static {
17        /// Returns the additive identity (0.0).
18        fn zero() -> Self;
19        /// Returns the multiplicative identity (1.0).
20        fn one() -> Self;
21        /// Cast a `usize` value to this scalar type.
22        fn from_usize(n: usize) -> Self;
23    }
24
25    impl<T: Float + core::fmt::Debug + Copy + 'static> Scalar for T {
26        fn zero() -> Self {
27            T::zero()
28        }
29        fn one() -> Self {
30            T::one()
31        }
32        fn from_usize(n: usize) -> Self {
33            num_traits::NumCast::from(n).unwrap_or(Self::one())
34        }
35    }
36}
37
38#[cfg(all(feature = "num-traits", not(feature = "std")))]
39mod inner {
40    use num_traits::float::FloatCore;
41
42    /// A scalar type suitable for arc-length, parameter, and distance computations.
43    ///
44    /// Requires `FloatCore` from `num-traits` plus `Debug`, `Copy`, and `'static` bounds.
45    /// Implementations are provided automatically for any type satisfying those bounds
46    /// (e.g. `f32`, `f64`).
47    pub trait Scalar: FloatCore + core::fmt::Debug + Copy + 'static {
48        /// Returns the additive identity (0.0).
49        fn zero() -> Self;
50        /// Returns the multiplicative identity (1.0).
51        fn one() -> Self;
52        /// Cast a `usize` value to this scalar type.
53        fn from_usize(n: usize) -> Self;
54    }
55
56    impl<T: FloatCore + core::fmt::Debug + Copy + 'static> Scalar for T {
57        fn zero() -> Self {
58            T::zero()
59        }
60        fn one() -> Self {
61            T::one()
62        }
63        fn from_usize(n: usize) -> Self {
64            num_traits::NumCast::from(n).unwrap_or(Self::one())
65        }
66    }
67}
68
69#[cfg(not(feature = "num-traits"))]
70mod inner {
71    /// A scalar type suitable for arc-length, parameter, and distance computations.
72    ///
73    /// Requires arithmetic operations (`Add`, `Sub`, `Mul`, `Div`, `Neg`),
74    /// `PartialOrd`, `Debug`, `Copy`, and `'static` bounds.
75    /// Manual implementations are provided for `f32` and `f64`.
76    pub trait Scalar:
77        core::ops::Add<Output = Self>
78        + core::ops::Sub<Output = Self>
79        + core::ops::Mul<Output = Self>
80        + core::ops::Div<Output = Self>
81        + core::ops::Neg<Output = Self>
82        + PartialOrd
83        + core::fmt::Debug
84        + Copy
85        + 'static
86    {
87        /// Returns the additive identity (0.0).
88        fn zero() -> Self;
89        /// Returns the multiplicative identity (1.0).
90        fn one() -> Self;
91        /// Cast a `usize` value to this scalar type.
92        fn from_usize(n: usize) -> Self;
93    }
94
95    macro_rules! impl_scalar {
96        ($($t:ty),+) => {
97            $(
98                impl Scalar for $t {
99                    fn zero() -> Self { 0.0 }
100                    fn one() -> Self { 1.0 }
101                    fn from_usize(n: usize) -> Self { n as $t }
102                }
103            )+
104        };
105    }
106
107    impl_scalar!(f32, f64);
108}
109
110pub use inner::Scalar;
path_traits/scalar.rs

path_traits/
scalar.rs
