fixed

commit 2af589212f68432f3a80fb20f615a04e9415489d
parent ebede50c1cb0d7f69338f4cc0a6adcc8638b2f1c
Author: Jared Tobin <jared@jtobin.io>
Date:   Wed, 22 Jan 2025 17:01:24 +0400

lib: quotrem_by1

Diffstat:
M
lib/Data/Word/Extended.hs
 | 
19
++++++++++++++-----
M
test/Main.hs
 | 
16
++++++++--------

2 files changed, 22 insertions(+), 13 deletions(-)
diff --git a/lib/Data/Word/Extended.hs b/lib/Data/Word/Extended.hs
@@ -244,8 +244,8 @@ sub_mul (Word256 x0 x1 x2 x3) (Word256 y0 y1 y2 y3) m =
 
 -- quotient, remainder of (hi, lo) divided by y
 -- translated from Div64 in go's math/bits package
-quot_rem_r :: Word64 -> Word64 -> Word64 -> W64Pair
-quot_rem_r hi lo y_0
+quotrem_r :: Word64 -> Word64 -> Word64 -> W64Pair
+quotrem_r hi lo y_0
     | y_0 == 0  = error "ppad-fixed: division by zero"
     | y_0 <= hi = error "ppad-fixed: overflow"
     | hi == 0   = P (lo `quot` y_0) (lo `rem` y_0)
@@ -289,10 +289,10 @@ quot_rem_r hi lo y_0
 
 recip_2by1 :: Word64 -> Word64
 recip_2by1 d = r where
-  !(P r _) = quot_rem_r (B.complement d) 0xffffffffffffffff d
+  !(P r _) = quotrem_r (B.complement d) 0xffffffffffffffff d
 
-quot_rem_2by1 :: Word64 -> Word64 -> Word64 -> Word64 -> W64Pair
-quot_rem_2by1 uh ul d rec =
+quotrem_2by1 :: Word64 -> Word64 -> Word64 -> Word64 -> W64Pair
+quotrem_2by1 uh ul d rec =
   let !(P qh_0 ql) = mul_c rec uh
       !(P ql_0 c)  = add_c ql ul 0
       !(P (succ -> qh_1) _)  = add_c qh_0 uh c
@@ -305,3 +305,12 @@ quot_rem_2by1 uh ul d rec =
       then P (qh_y + 1) (r_y - d)
       else P qh_y r_y
 
+quotrem_by1 :: Word256 -> Word64 -> Word256WithOverflow
+quotrem_by1 (Word256 u0 u1 u2 u3) d =
+  let !rec = recip_2by1 d
+      !r0  = u3
+      !(P q2 r1) = quotrem_2by1 r0 u2 d rec
+      !(P q1 r2) = quotrem_2by1 r1 u1 d rec
+      !(P q0 r3) = quotrem_2by1 r2 u0 d rec
+  in  Word256WithOverflow (Word256 q0 q1 q2 0) r3
+
diff --git a/test/Main.hs b/test/Main.hs
@@ -105,14 +105,14 @@ mul_512_matches (Q.NonNegative a) (Q.NonNegative b) =
 
 -- assertions ------------------------------------------------------------------
 
-quot_rem_r_case0 :: H.Assertion
-quot_rem_r_case0 = do
-  let !(P q r) = quot_rem_r 2 4 4
+quotrem_r_case0 :: H.Assertion
+quotrem_r_case0 = do
+  let !(P q r) = quotrem_r 2 4 4
   H.assertEqual mempty (P 9223372036854775809 0) (P q r)
 
-quot_rem_r_case1 :: H.Assertion
-quot_rem_r_case1 = do
-  let !(P q r) = quot_rem_r 0 4 2
+quotrem_r_case1 :: H.Assertion
+quotrem_r_case1 = do
+  let !(P q r) = quotrem_r 0 4 2
   H.assertEqual mempty (P 2 0) (P q r)
 
 recip_2by1_case0 :: H.Assertion
@@ -166,8 +166,8 @@ main = defaultMain $
     , arithmetic
     ]
   , testGroup "unit tests" [
-      H.testCase "quot_rem_r matches case0" quot_rem_r_case0
-    , H.testCase "quot_rem_r matches case1" quot_rem_r_case1
+      H.testCase "quotrem_r matches case0" quotrem_r_case0
+    , H.testCase "quotrem_r matches case1" quotrem_r_case1
     , H.testCase "recip_2by1 matches case0" recip_2by1_case0
     , H.testCase "recip_2by1 matches case1" recip_2by1_case1
     ]