diff --git a/cmd/sqrtRepetend.go b/cmd/sqrtRepetend.go
index d6292e8..a99a676 100644
--- a/cmd/sqrtRepetend.go
+++ b/cmd/sqrtRepetend.go
@@ -17,46 +17,14 @@ along with this program. If not, see <http://www.gnu.org/licenses/>.
 package cmd
 
 import (
-	"errors"
 	"fmt"
 	"log"
 	"math/big"
 
 	"github.com/spf13/cobra"
+	"scm.dairydemon.net/filifa/mathtools/internal/lib"
 )
 
-func computeSqrtRepetend(x *big.Int) ([]*big.Int, error) {
-	m := big.NewInt(0)
-	d := big.NewInt(1)
-	a0 := new(big.Int).Sqrt(x)
-
-	s := new(big.Int).Exp(a0, big.NewInt(2), nil)
-	if x.Cmp(s) == 0 {
-		return nil, errors.New("input is a perfect square")
-	}
-
-	repetend := make([]*big.Int, 0)
-
-	a := new(big.Int).Set(a0)
-	twoa0 := new(big.Int).Mul(big.NewInt(2), a0)
-	for a.Cmp(twoa0) != 0 {
-		// m = d * a - m
-		tmp := new(big.Int)
-		m.Sub(tmp.Mul(d, a), m)
-
-		// d = (x - m^2) // d
-		tmp.Exp(m, big.NewInt(2), nil)
-		d.Div(tmp.Sub(x, tmp), d)
-
-		// a = (a0 + m) // d
-		a.Div(tmp.Add(a0, m), d)
-
-		repetend = append(repetend, new(big.Int).Set(a))
-	}
-
-	return repetend, nil
-}
-
 func sqrtRepetend(cmd *cobra.Command, args []string) {
 	x := new(big.Int)
 
@@ -67,7 +35,7 @@ func sqrtRepetend(cmd *cobra.Command, args []string) {
 			continue
 		}
 
-		repetend, err := computeSqrtRepetend(x)
+		repetend, err := lib.SqrtRepetend(x)
 		if err != nil {
 			log.Print(s + " is a perfect square")
 			continue
diff --git a/internal/lib/lib.go b/internal/lib/lib.go
new file mode 100644
index 0000000..66d2eb6
--- /dev/null
+++ b/internal/lib/lib.go
@@ -0,0 +1,38 @@
+package lib
+
+import (
+	"errors"
+	"math/big"
+)
+
+func SqrtRepetend(x *big.Int) ([]*big.Int, error) {
+	m := big.NewInt(0)
+	d := big.NewInt(1)
+	a0 := new(big.Int).Sqrt(x)
+
+	s := new(big.Int).Exp(a0, big.NewInt(2), nil)
+	if x.Cmp(s) == 0 {
+		return nil, errors.New("input is a perfect square")
+	}
+
+	repetend := make([]*big.Int, 0)
+
+	a := new(big.Int).Set(a0)
+	twoa0 := new(big.Int).Mul(big.NewInt(2), a0)
+	for a.Cmp(twoa0) != 0 {
+		// m = d * a - m
+		tmp := new(big.Int)
+		m.Sub(tmp.Mul(d, a), m)
+
+		// d = (x - m^2) // d
+		tmp.Exp(m, big.NewInt(2), nil)
+		d.Div(tmp.Sub(x, tmp), d)
+
+		// a = (a0 + m) // d
+		a.Div(tmp.Add(a0, m), d)
+
+		repetend = append(repetend, new(big.Int).Set(a))
+	}
+
+	return repetend, nil
+}