ggmath 0.17.1

A linear algebra library for games and graphics with generic SIMD types.
Documentation 
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use crate::PrimitiveFloat;

#[cfg(feature = "wide")]
mod wide;

/// Extends floating-point primitives with extra functionality.
#[expect(private_bounds)]
pub trait FloatExt: Sealed {
    /// Computes the linear interpolation between `self` and `other` based on
    /// the value `t`.
    ///
    /// When `t` is `0.0`, the result is `self`.  When `t` is `1.0`, the result
    /// is `other`. When `t` is outside of the range `0.0..=1.0`, the result is
    /// linearly extrapolated.
    #[must_use]
    fn lerp(self, other: Self, t: Self) -> Self;

    /// Moves `self` towards `other` by at most `max_delta`.
    ///
    /// When `max_delta` is `0`, the result is `self`. When `max_delta` is equal
    /// to or greater than `(self - target).abs()`, the result is `target`.
    ///
    /// ```
    /// # use ggmath::FloatExt;
    /// #
    /// assert_eq!(2.0.move_towards(5.0, 1.0), 3.0);
    /// assert_eq!(2.0.move_towards(-5.0, 1.0), 1.0);
    /// ```
    #[must_use]
    fn move_towards(self, target: Self, max_delta: Self) -> Self;

    /// Returns `true` if the absolute difference between `self` and `other` is
    /// less than or equal to `max_abs_diff`.
    ///
    /// This can be used to compare two values that should be equal, but may
    /// have a slight difference due to operations having rounding errors.
    #[must_use]
    fn abs_diff_eq(self, other: Self, max_abs_diff: Self) -> bool;
}

trait Sealed {}

impl<T: PrimitiveFloat> FloatExt for T {
    #[inline]
    fn lerp(self, other: Self, t: Self) -> Self {
        self * (T::ONE - t) + other * t
    }

    #[inline]
    fn move_towards(self, target: Self, max_delta: Self) -> Self {
        let delta = target - self;
        let delta_abs = delta.abs();

        if delta_abs <= max_delta || delta_abs <= Self::as_from(1e-4) {
            target
        } else {
            self + max_delta * delta.signum()
        }
    }

    #[inline]
    fn abs_diff_eq(self, other: Self, max_abs_diff: Self) -> bool {
        (self - other).abs() <= max_abs_diff
    }
}

impl<T: PrimitiveFloat> Sealed for T {}

#[cfg(test)]
mod tests {
    use crate::{
        FloatExt,
        test_utils::{assert_test_eq, for_types, random_iter},
    };

    #[test]
    fn test_lerp() {
        for_types!(|T: PrimitiveFloat| {
            for [x, y] in
                random_iter::<[T; 2]>().filter(|values| values.iter().all(|x| x.is_finite()))
            {
                assert_test_eq!(x.lerp(y, 0.0), x, 0.0 = -0.0);
                assert_test_eq!(x.lerp(y, 0.5), x * 0.5 + y * 0.5, 0.0 = -0.0);
                assert_test_eq!(x.lerp(y, 1.0), y, 0.0 = -0.0);
            }
        });
    }

    #[test]
    fn test_move_towards() {
        for_types!(|T: PrimitiveFloat| {
            assert!(T::abs_diff_eq(5.0.move_towards(10.0, 2.0), 7.0, 1e-5));
            assert!(T::abs_diff_eq(10.0.move_towards(5.0, 2.0), 8.0, 1e-5));
            assert!(T::abs_diff_eq((-5.0).move_towards(10.0, 2.0), -3.0, 1e-5));
            assert!(T::abs_diff_eq(10.0.move_towards(-5.0, 2.0), 8.0, 1e-5));
            assert!(T::abs_diff_eq(5.0.move_towards(10.0, 20.0), 10.0, 1e-5));
            assert!(T::abs_diff_eq(10.0.move_towards(5.0, 20.0), 5.0, 1e-5));
            assert!(T::abs_diff_eq((-5.0).move_towards(10.0, 20.0), 10.0, 1e-5));
            assert!(T::abs_diff_eq(10.0.move_towards(-5.0, 20.0), -5.0, 1e-5));
        });
    }

    #[test]
    fn test_abs_diff_eq() {
        for_types!(|T: PrimitiveFloat| {
            assert!(T::abs_diff_eq(0.0, 0.0, 0.125));
            assert!(T::abs_diff_eq(0.0, 0.1, 0.125));
            assert!(T::abs_diff_eq(5.0, 4.9, 0.125));
            assert!(!T::abs_diff_eq(0.0, 1.0, 0.125));
            assert!(!T::abs_diff_eq(0.0, 0.9, 0.125));
            assert!(!T::abs_diff_eq(5.0, 3.9, 0.125));
        });
    }
}