From 6fd30289569f72df0ba2d27ae3b7048cdbf354d7 Mon Sep 17 00:00:00 2001
From: Henry de Valence <hdevalence@hdevalence.ca>
Date: Tue, 31 Jan 2017 17:19:34 -0500
Subject: [PATCH] Add constant for 4*d

---
 src/constants.rs | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/src/constants.rs b/src/constants.rs
index 09f1772..1607258 100644
--- a/src/constants.rs
+++ b/src/constants.rs
@@ -29,6 +29,9 @@ pub const d: FieldElement       = FieldElement([
 pub const d2: FieldElement      = FieldElement([
     -21827239,  -5839606, -30745221,  13898782,    229458,
     15978800,  -12551817,  -6495438,  29715968,   9444199, ]);
+pub const d4: FieldElement      = FieldElement([
+    23454405,  -11679213,   5618422,  -5756869,    458917,
+    -1596832,  -25103633, -12990876,  -7676928, -14666033  ]);
 
 /// Precomputed value of one of the square roots of -1 (mod p)
 pub const SQRT_M1: FieldElement = FieldElement([
@@ -1520,6 +1523,13 @@ mod test {
         assert_eq!(d2, constants::d2);
     }
 
+    #[test]
+    fn test_d4() {
+        let mut four = FieldElement::zero();
+        four[0] = 4;
+        assert_eq!(&constants::d * &four, constants::d4);
+    }
+
     /// Test the values in the lookup table of precomputed multiples
     /// of the basepoint.
     #[test]