Function isclose 

pub fn isclose(a: f64, b: f64, rel_tol: f64, abs_tol: f64) -> bool

Approximate equality with relative and absolute tolerances.

|a - b| <= abs_tol + rel_tol * max(|a|, |b|); NaNs never compare close.

use mathverse_core::float::isclose;
assert!(isclose(0.1 + 0.2, 0.3, 1e-9, 1e-12));
assert!(!isclose(1.0, 2.0, 1e-9, 1e-12));