//! Constants used for numerical differentiation.
usestd::sync::LazyLock;/// Square root of the machine epsilon ($\sqrt{\varepsilon}$).
pubstaticSQRT_EPS:LazyLock<f64>=LazyLock::new(||f64::EPSILON.sqrt());/// Cube root of the machine epsilon ($\varepsilon^{1/3}$).
pubstaticCBRT_EPS:LazyLock<f64>=LazyLock::new(||f64::EPSILON.cbrt());