pub fn gauss_legendre<F: FnMut(f64) -> f64>(f: F, a: f64, b: f64) -> f64Expand description
Integrate f over [a, b] with the fixed ten-point rule.
Exact for polynomials up to degree nineteen. No error estimate; for that,
use integrate, which is this applied adaptively.
A reversed interval integrates to the negative, as it should: the rule
carries the sign of b - a rather than quietly sorting its arguments.