From 74744095f1666e08441b3aeb1d16ebbdf3eff600 Mon Sep 17 00:00:00 2001
From: Timothy Warren <twarren@nabancard.com>
Date: Wed, 11 Mar 2020 14:01:45 -0400
Subject: [PATCH] Fix zero subtraction
---
src/bigint.rs | 14 ++++----------
1 file changed, 4 insertions(+), 10 deletions(-)
diff --git a/src/bigint.rs b/src/bigint.rs
index c47bf88..1e6cf67 100644
--- a/src/bigint.rs
+++ b/src/bigint.rs
@@ -175,15 +175,9 @@ impl Sub for BigInt {
let a = *self.inner.get(i).unwrap_or(&0usize);
let b = *rhs.inner.get(i).unwrap_or(&0usize);
- if a > 0 && (a - borrow) >= b {
+ if a >= borrow && (a - borrow) >= b {
let res = a - b - borrow;
- // Don't add an extra zero if you borrowed everything
- // from the most significant digit
- if res == 0 && digits > 0 && i == digits -1 {
- return out;
- }
-
out.inner.push(res);
borrow = 0;
} else {
@@ -462,9 +456,9 @@ mod tests {
let a = BigInt::new();
let b = BigInt::new();
- // let c = a.clone() - b.clone();
- // assert_eq!(a.clone(), b.clone());
- // assert_eq!(c, a.clone());
+ let c = a.clone() - b.clone();
+ assert_eq!(a.clone(), b.clone());
+ assert_eq!(c, a.clone());
let c = a.clone() + b.clone();
assert_eq!(a.clone(), b.clone());