#[macro_export]
macro_rules! assert_almost_eq {
($a:expr, $b:expr, $prec:expr) => (
let diff = ($a - $b).abs();
if diff > $prec {
panic!(format!(
"assertion failed: `abs(left - right) = {:.1e} < {:e}`, \
(left: `{}`, right: `{}`)",
diff, $prec, $a, $b));
}
);
}