From c55a1956d44f4e4b0fc15f466db9d763a106ebee Mon Sep 17 00:00:00 2001
From: Adam Wick <awick@uhsure.com>
Date: Sun, 30 Dec 2018 17:14:52 -0800
Subject: [PATCH] Add support for modular division with negative divisors.

---
 src/signed/moddiv.rs    | 9 +--------
 test-generator/Tests.hs | 3 ++-
 2 files changed, 3 insertions(+), 9 deletions(-)

diff --git a/src/signed/moddiv.rs b/src/signed/moddiv.rs
index e62e51e..6943797 100644
--- a/src/signed/moddiv.rs
+++ b/src/signed/moddiv.rs
@@ -11,10 +11,9 @@ macro_rules! moddiv_impls {
         impl ModDiv for $sname {
             fn moddiv(&self, divisor: &Self, phi: &Self) -> Self
             {
-                assert!(!divisor.is_negative());
                 let safe_divisor = divisor % phi;
                 let unsigned_i = safe_divisor.value.modinv(&phi.value).expect("no modular inverse of moddiv divisor");
-                let i = $sname::new(false, unsigned_i);
+                let i = $sname::new(divisor.negative, unsigned_i);
                 let selfi = i * self;
                 $sname::from( selfi % $dbl::from(phi) )
             }
@@ -50,12 +49,6 @@ macro_rules! generate_moddiv_tests {
             let m = $sname::new(*negm, $tname::from_bytes(mbytes));
             let c = $sname::new(*negc, $tname::from_bytes(cbytes));
             let res = a.moddiv(&b, &m);
-            println!("-------------");
-            println!("a: {:x}", a);
-            println!("b: {:x}", b);
-            println!("m: {:x}", m);
-            println!("c: {:x}", c);
-            println!("r: {:x}", res);
             assert_eq!(c, res);
         });
     };
diff --git a/test-generator/Tests.hs b/test-generator/Tests.hs
index 2fb1d85..ca5696c 100644
--- a/test-generator/Tests.hs
+++ b/test-generator/Tests.hs
@@ -38,6 +38,7 @@ testDatabase = [
     (SignedCmp,   "sigcmp",         "signed compare",          sigcmpTest),
     (SignedMul,   "sigmul",         "signed multiply",         sigmulTest),
     (SignedDiv,   "sigdiv",         "signed division",         sigdivTest),
+    (SignedModInv,"smodinv",        "signed modular inversion",smodinvTest),
     (SignedShift, "sigshiftr",      "signed shift right",      sigshiftrTest),
     (SignedShift, "sigshiftl",      "signed shift left",       sigshiftlTest),
     (SignedSub,   "sigsub",         "signed subtraction",      sigsubTest),
@@ -287,7 +288,7 @@ moddivTest :: Test
 moddivTest size memoryIn =
   let attempt memory0 =
         let (a, memory1) = genSign (generateNum memory0 "a" size)
-            (b, memory2) = generateNum memory1 "b" size
+            (b, memory2) = genSign (generateNum memory1 "b" size)
             (m, memory3) = generateNum memory2 "m" size
             maybe_res    = divmod a b m
         in case maybe_res of