From 27f745ee6d2f9d3e4d28a5b8b1b28f97db4dff08 Mon Sep 17 00:00:00 2001
From: Hexa Dust <hxd@hexadust.net>
Date: Fri, 18 Jul 2025 21:19:30 +0100
Subject: [PATCH] assert significant is valid

---
 src/lib.rs | 37 ++++++++++++++++++++++++++++++-------
 1 file changed, 30 insertions(+), 7 deletions(-)

diff --git a/src/lib.rs b/src/lib.rs
index bd59c63..de2e8c4 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -23,14 +23,35 @@ impl Display for DecimalError {
 
 #[derive(Debug, Clone, Copy, PartialEq, Eq)]
 pub struct Decimal<const SIZE: usize = 5, EXP = u16> {
-    pub minus: bool,
-    pub significant: [u8; SIZE],
-    pub minus_exponent: bool,
-    pub exponent: EXP,
+    minus: bool,
+    significant: [u8; SIZE],
+    minus_exponent: bool,
+    exponent: EXP,
 }
 
 impl<const SIZE: usize, EXP: PrimInt + Unsigned> Decimal<SIZE, EXP> {
-    pub fn from_float<F: FloatCore>(mut f: F) -> Result<Decimal<SIZE, EXP>, DecimalError> {
+    pub fn new(minus: bool, significant: [u8; SIZE], minus_exponent: bool, exponent: EXP) -> Self {
+        for s in significant {
+            assert!(s < 10, "bad significant");
+        }
+        Decimal {
+            minus,
+            significant,
+            minus_exponent,
+            exponent,
+        }
+    }
+
+    pub fn into_parts(self) -> (bool, [u8; SIZE], bool, EXP) {
+        (
+            self.minus,
+            self.significant,
+            self.minus_exponent,
+            self.exponent,
+        )
+    }
+
+    pub fn from_float<F: FloatCore>(mut f: F) -> Result<Self, DecimalError> {
         if !f.is_finite() {
             return Err(DecimalError::NotANumber);
         }
@@ -57,10 +78,12 @@ impl<const SIZE: usize, EXP: PrimInt + Unsigned> Decimal<SIZE, EXP> {
         }
         let mut significant = [0; SIZE];
         for i in 0..SIZE {
-            let s = f.trunc().to_u8().unwrap();
+            let mut s = f.trunc().to_u8().unwrap();
+            if s >= 10 {
+                s = 9;
+            }
             f = f * F::from(10).unwrap();
             f = f - F::from(s * 10).ok_or(DecimalError::ExponentOverflow)?;
-            debug_assert!(s < 10);
             significant[i] = s;
         }
         Ok(Decimal {