Fix Hurwitz integer prod issue.

Signed-off-by: txaty <[email protected]>

Author: txaty

hurwitz_integer.go

@@ -301,48 +301,44 @@ func (h *HurwitzInt) Prod(a, b *HurwitzInt) *HurwitzInt {
 	if h.dblR == nil {
 		h.dblR = new(big.Int)
 	}
-	r := h.dblR
 	if h.dblI == nil {
 		h.dblI = new(big.Int)
 	}
-	i := h.dblI
 	if h.dblJ == nil {
 		h.dblJ = new(big.Int)
 	}
-	j := h.dblJ
 	if h.dblK == nil {
 		h.dblK = new(big.Int)
 	}
-	k := h.dblK
 	opt := iPool.Get().(*big.Int)
 	defer iPool.Put(opt)
 	// 1 part
-	r.Mul(a.dblR, b.dblR)
-	r.Sub(r, opt.Mul(a.dblI, b.dblI))
-	r.Sub(r, opt.Mul(a.dblJ, b.dblJ))
-	r.Sub(r, opt.Mul(a.dblK, b.dblK))
-	r.Rsh(r, 1)
+	h.dblR.Mul(a.dblR, b.dblR)
+	h.dblR.Sub(h.dblR, opt.Mul(a.dblI, b.dblI))
+	h.dblR.Sub(h.dblR, opt.Mul(a.dblJ, b.dblJ))
+	h.dblR.Sub(h.dblR, opt.Mul(a.dblK, b.dblK))
+	h.dblR.Rsh(h.dblR, 1)
 
 	// i part
-	i.Mul(a.dblR, b.dblI)
-	i.Add(i, opt.Mul(a.dblI, b.dblR))
-	i.Add(i, opt.Mul(a.dblJ, b.dblK))
-	i.Sub(i, opt.Mul(a.dblK, b.dblJ))
-	i.Rsh(i, 1)
+	h.dblI.Mul(a.dblR, b.dblI)
+	h.dblI.Add(h.dblI, opt.Mul(a.dblI, b.dblR))
+	h.dblI.Add(h.dblI, opt.Mul(a.dblJ, b.dblK))
+	h.dblI.Sub(h.dblI, opt.Mul(a.dblK, b.dblJ))
+	h.dblI.Rsh(h.dblI, 1)
 
 	// j part
-	j.Mul(a.dblR, b.dblJ)
-	j.Sub(j, opt.Mul(a.dblI, b.dblK))
-	j.Add(j, opt.Mul(a.dblJ, b.dblR))
-	j.Add(j, opt.Mul(a.dblK, b.dblI))
-	j.Rsh(j, 1)
+	h.dblJ.Mul(a.dblR, b.dblJ)
+	h.dblJ.Sub(h.dblJ, opt.Mul(a.dblI, b.dblK))
+	h.dblJ.Add(h.dblJ, opt.Mul(a.dblJ, b.dblR))
+	h.dblJ.Add(h.dblJ, opt.Mul(a.dblK, b.dblI))
+	h.dblJ.Rsh(h.dblJ, 1)
 
 	// k part
-	k.Mul(a.dblR, b.dblK)
-	k.Add(k, opt.Mul(a.dblI, b.dblJ))
-	k.Sub(k, opt.Mul(a.dblJ, b.dblI))
-	k.Add(k, opt.Mul(a.dblK, b.dblR))
-	k.Rsh(k, 1)
+	h.dblK.Mul(a.dblR, b.dblK)
+	h.dblK.Add(h.dblK, opt.Mul(a.dblI, b.dblJ))
+	h.dblK.Sub(h.dblK, opt.Mul(a.dblJ, b.dblI))
+	h.dblK.Add(h.dblK, opt.Mul(a.dblK, b.dblR))
+	h.dblK.Rsh(h.dblK, 1)
 
 	return h
 }

hurwitz_integer_test.go

@@ -24,7 +24,7 @@ func TestHurwitzInt_Prod(t *testing.T) {
 		want   *HurwitzInt
 	}{
 		{
-			name: "test_(1+i+j+k)+(1+i+j+k)",
+			name: "test_(1+i+j+k) * (1+i+j+k)",
 			fields: fields{
 				dblR: nil,
 				dblI: nil,
@@ -37,6 +37,20 @@ func TestHurwitzInt_Prod(t *testing.T) {
 			},
 			want: NewHurwitzInt(big.NewInt(-2), big.NewInt(2), big.NewInt(2), big.NewInt(2), false),
 		},
+		{
+			name: "test_2i * 1",
+			fields: fields{
+				dblR: nil,
+				dblI: nil,
+				dblJ: nil,
+				dblK: nil,
+			},
+			args: args{
+				a: NewHurwitzInt(big.NewInt(0), big.NewInt(2), big.NewInt(0), big.NewInt(0), false),
+				b: NewHurwitzInt(big.NewInt(1), big.NewInt(0), big.NewInt(0), big.NewInt(0), false),
+			},
+			want: NewHurwitzInt(big.NewInt(0), big.NewInt(2), big.NewInt(0), big.NewInt(0), false),
+		},
 	}
 	for _, tt := range tests {
 		t.Run(tt.name, func(t *testing.T) {