Handle zero and negative values in adjust_approximate

Author: YichiZhang0613

factorion-math/src/lib.rs

@@ -336,11 +336,13 @@ pub fn approximate_termial_digits_float(k: u32, n: Float) -> Integer {
 /// Adjusts the output of [`approximate_factorial`], by combining the 10 exponents of the number and the extra exponent.
 ///
 /// # Panic
-/// Will panic if `x` is not finite or `x` is non-positive.
+/// Will panic if `x` is not finite.
 pub fn adjust_approximate((x, e): (Float, Integer)) -> (Float, Integer) {
-    assert!(x > 0.0, "Got non-positive number, x was {x}");
     let prec = x.prec();
-    let (extra, _) = (x.clone().ln() / Float::with_val(prec, 10).ln())
+    if x == 0.0 {
+        return (Float::with_val(prec, 0), Integer::ZERO.clone());
+    }
+    let (extra, _) = (x.clone().abs().ln() / Float::with_val(prec, 10).ln())
         .to_integer_round(rug::float::Round::Down)
         .unwrap_or_else(|| panic!("Got non-finite number, x was {x}"));
     let x = x / (Float::with_val(prec, 10).pow(extra.clone()));