matrix/mat64: reverse API signatures for matrix extraction

matrix/mat64/qr_test.go

@@ -30,16 +30,16 @@ func TestQR(t *testing.T) {
 		var want Dense
 		want.Clone(a)
 
-		qr := &QR{}
+		var qr QR
 		qr.Factorize(a)
 		var q, r Dense
-		q.QFromQR(qr)
+		qr.QTo(&q)
 
 		if !isOrthonormal(&q, 1e-10) {
 			t.Errorf("Q is not orthonormal: m = %v, n = %v", m, n)
 		}
 
-		r.RFromQR(qr)
+		qr.RTo(&r)
 
 		var got Dense
 		got.Mul(&q, &r)