1 files changed, 7 insertions, 10 deletions
diff --git a/src/eval.rs b/src/eval.rs
index 470bae6..1045b17 100644
--- a/src/eval.rs
+++ b/src/eval.rs
@@ -1,6 +1,5 @@
 use num::pow::Pow;
 use num::{BigInt, FromPrimitive, Integer, Signed, ToPrimitive};
-use std::cmp::Ordering;
 use std::fmt::{Display, Formatter};
 
 pub enum Num {
@@ -194,6 +193,10 @@ impl Num {
     }
 }
 
+fn log10(n: &BigInt) -> u64 {
+    ((n.bits() - 1) as f64 / std::f64::consts::LOG2_10) as u64
+}
+
 impl Display for Num {
     fn fmt(&self, f: &mut Formatter<'_>) -> Result<(), std::fmt::Error> {
         match self {
@@ -201,21 +204,15 @@ impl Display for Num {
                 if n.bits() < 100 {
                     return write!(f, "{n}");
                 }
-                let buf = format!("{n}");
-                let rounding_factor = BigInt::from(10).pow(buf.len() - 8);
-                let (mut rounded, rem) = n.div_mod_floor(&rounding_factor);
-                match rem.cmp(&(rounding_factor / 2)) {
-                    Ordering::Greater => rounded += 1,
-                    Ordering::Equal if rounded.is_odd() => rounded += 1,
-                    _ => (),
-                }
+                let len = log10(n) + 1;
+                let rounded = i64::try_from(n / BigInt::from(10).pow(len - 8)).unwrap();
                 let rounded_str = format!("{rounded}");
                 write!(
                     f,
                     "{}.{}e{}",
                     &rounded_str[..1],
                     &rounded_str[1..],
-                    buf.len() - 1
+                    len - 8 + rounded_str.len() as u64 - 1
                 )
             }
             Num::Float(n) => {