implements instance EuclideanRing

.gitignore

@@ -8,3 +8,4 @@
 /.purs*
 /.psa*
 /.spago
+/package-lock.json

src/Js/BigInt/BigInt.js

@@ -25,7 +25,23 @@ export const biMul = (x) => (y) => x * y;
 
 export const biSub = (x) => (y) => x - y;
 
-export const biMod = (x) => (y) => x % y;
+export const biMod = (x) => (y) => {
+  if (y === 0n)
+    return 0n;
+  const yy = y < 0n ? -y : y;
+  return ((x % yy) + yy) % yy;
+}
+
+export const biDiv = (x) => (y) => {
+  if (y === 0n) return 0n;
+  const xx = x - biMod(x)(y);
+  return y > 0n ? (xx / y) : -(xx / -y);
+}
+
+export const biDegree = (x) => {
+  const xx = x < 0n ? -x : x;
+  return BigInt.asIntN(32, xx > 2147483647n ? 2147483647n : xx);
+}
 
 export const biZero = 0n;
 

src/Js/BigInt/BigInt.purs

@@ -91,10 +91,18 @@ foreign import biSub :: BigInt -> BigInt -> BigInt
 instance Ring BigInt where
   sub = biSub
 
+
 foreign import biMod :: BigInt -> BigInt -> BigInt
+foreign import biDiv :: BigInt -> BigInt -> BigInt
+foreign import biDegree :: BigInt -> Int
 
 instance CommutativeRing BigInt
 
+instance EuclideanRing BigInt where
+  degree = biDegree
+  div = biDiv
+  mod = biMod
+
 -- Raise an BigInt to the power of another BigInt.
 foreign import pow :: BigInt -> BigInt -> BigInt
 

test/Main.purs

@@ -7,7 +7,7 @@ import Debug (spy)
 import Effect (Effect)
 import Effect.Console (log)
 import Js.BigInt.BigInt (BigInt, and, fromInt, fromString, fromTLInt, not, or, pow, shl, shr, toString, xor)
-import Prelude (class CommutativeRing, class Eq, class Ord, class Ring, class Semiring, Unit, bind, compare, discard, identity, map, negate, one, pure, show, zero, ($), (*), (+), (-), (<$>), (<<<), (==))
+import Prelude (class CommutativeRing, class Eq, class EuclideanRing, class Ord, class Ring, class Semiring, Unit, bind, compare, discard, identity, map, negate, one, pure, show, zero, ($), (*), (+), (-), (<$>), (<<<), (==))
 import Test.Assert (assert)
 import Test.QuickCheck (quickCheck)
 import Test.QuickCheck.Arbitrary (class Arbitrary)
@@ -32,6 +32,7 @@ derive newtype instance Ord TestBigInt
 derive newtype instance Semiring TestBigInt
 derive newtype instance Ring TestBigInt
 derive newtype instance CommutativeRing TestBigInt
+derive newtype instance EuclideanRing TestBigInt
 
 instance Arbitrary TestBigInt where
   arbitrary = do
@@ -118,6 +119,7 @@ main = do
   Data.checkSemiring prxBigInt
   Data.checkRing prxBigInt
   Data.checkCommutativeRing prxBigInt
+  -- Data.checkEuclideanRing prxBigInt
 
   log "Converting BigInt to Int"
   -- assert $ (fromString "0" <#> asIntN 64) == Just 0