From a9ac2b95f485c31e40273dee7f09dcfff8340777 Mon Sep 17 00:00:00 2001
From: Brendan Zabarauskas <bjzaba@yahoo.com.au>
Date: Tue, 7 May 2013 14:36:32 +1000
Subject: Add abs_sub method to Signed trait

---
 src/libstd/num/bigint.rs | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

(limited to 'src/libstd')

diff --git a/src/libstd/num/bigint.rs b/src/libstd/num/bigint.rs
index cd347098e25..a5cf929ed93 100644
--- a/src/libstd/num/bigint.rs
+++ b/src/libstd/num/bigint.rs
@@ -831,6 +831,11 @@ impl Signed for BigInt {
         }
     }
 
+    #[inline(always)]
+    fn abs_sub(&self, other: &BigInt) -> BigInt {
+        if *self <= *other { Zero::zero() } else { *self - *other }
+    }
+
     #[inline(always)]
     fn signum(&self) -> BigInt {
         match self.sign {
@@ -1920,6 +1925,15 @@ mod bigint_tests {
         check(11, 5, 55);
     }
 
+    #[test]
+    fn test_abs_sub() {
+        assert_eq!((-One::one::<BigInt>()).abs_sub(&One::one()), Zero::zero());
+        assert_eq!(One::one::<BigInt>().abs_sub(&One::one()), Zero::zero());
+        assert_eq!(One::one::<BigInt>().abs_sub(&Zero::zero()), One::one());
+        assert_eq!(One::one::<BigInt>().abs_sub(&-One::one::<BigInt>()),
+                   IntConvertible::from_int(2));
+    }
+
     #[test]
     fn test_to_str_radix() {
         fn check(n: int, ans: &str) {
-- 
cgit 1.4.1-3-g733a5