axiolid_core/
scalar.rs

1//! Scalar storage and explicit tolerance policy.
2
3use core::fmt;
4
5/// Coordinate scalar stored by the format-neutral model.
6///
7/// `f64` preserves millimetre detail at national-grid coordinates. A backend may
8/// use narrower arithmetic internally only when its reported precision and the
9/// requested tolerance make that safe.
10pub type Scalar = f64;
11
12/// Invalid tolerance input.
13#[derive(Debug, Clone, Copy, PartialEq, Eq)]
14pub enum ToleranceError {
15    /// A component was negative, infinite, or NaN.
16    NotFiniteAndNonNegative,
17}
18
19impl fmt::Display for ToleranceError {
20    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
21        match self {
22            Self::NotFiniteAndNonNegative => {
23                f.write_str("tolerance values must be finite and non-negative")
24            }
25        }
26    }
27}
28
29impl std::error::Error for ToleranceError {}
30
31/// Linear and angular tolerance carried with an operation.
32///
33/// There is deliberately no [`Default`] implementation: a useful tolerance is
34/// a property of the source unit scale and requested accuracy, not the crate.
35#[derive(Debug, Clone, Copy, PartialEq)]
36pub struct Tolerance {
37    linear: Scalar,
38    angular: Scalar,
39}
40
41impl Tolerance {
42    /// Exact-coordinate policy. Use only when the caller intentionally wants no
43    /// scale-derived tolerance, such as compatibility validation of an existing
44    /// source model.
45    pub const ZERO: Self = Self {
46        linear: 0.0,
47        angular: 0.0,
48    };
49
50    /// One micrometre linear and one nanoradian angular tolerance when geometry
51    /// has already been normalized to metres.
52    pub const METRE: Self = Self {
53        linear: 1e-6,
54        angular: 1e-9,
55    };
56
57    /// One micrometre linear and one nanoradian angular tolerance while values
58    /// are still expressed in millimetres.
59    pub const MILLIMETRE: Self = Self {
60        linear: 1e-3,
61        angular: 1e-9,
62    };
63
64    /// Construct a validated policy.
65    pub fn new(linear: Scalar, angular: Scalar) -> Result<Self, ToleranceError> {
66        if !linear.is_finite() || !angular.is_finite() || linear < 0.0 || angular < 0.0 {
67            return Err(ToleranceError::NotFiniteAndNonNegative);
68        }
69        Ok(Self { linear, angular })
70    }
71
72    /// Absolute distance tolerance in the model's current length unit.
73    #[inline]
74    pub const fn linear(self) -> Scalar {
75        self.linear
76    }
77
78    /// Absolute angular tolerance in radians.
79    #[inline]
80    pub const fn angular(self) -> Scalar {
81        self.angular
82    }
83
84    /// Compare two scalar values using the linear component.
85    #[inline]
86    pub fn eq(self, a: Scalar, b: Scalar) -> bool {
87        (a - b).abs() <= self.linear
88    }
89}
90
91#[cfg(test)]
92mod tests {
93    use super::*;
94
95    #[test]
96    fn rejects_invalid_policy() {
97        assert_eq!(
98            Tolerance::new(Scalar::NAN, 0.0),
99            Err(ToleranceError::NotFiniteAndNonNegative)
100        );
101        assert_eq!(
102            Tolerance::new(-1.0, 0.0),
103            Err(ToleranceError::NotFiniteAndNonNegative)
104        );
105    }
106
107    #[test]
108    fn policy_has_no_context_free_default() {
109        assert!(Tolerance::METRE.eq(1.0, 1.0 + 0.5e-6));
110        assert!(!Tolerance::METRE.eq(1.0, 1.0 + 2.0e-6));
111    }
112}
axiolid_core/scalar.rs

axiolid_core/
scalar.rs
