continuous sqrt now uses a slice internally

@@ -31,28 +31,23 @@ impl Continuous {
     // https://en.wikipedia.org/wiki/Methods_of_computing_square_roots#
     //  Continued_fraction_expansion
     pub fn sqrt(x :i64, a0 :i64) -> Self {
-        fn inner(mut v :Vec<i64>,
-                 x     :i64,
-                 a0    :i64,
-                 mn    :i64,
-                 dn    :i64,
-                 an    :i64) -> Vec<i64> {
+        fn inner(v :&mut [i64], x :i64, a0 :i64, mn :i64, dn :i64, an :i64) {
             let mn_1 = dn * an - mn;
             let dn_1 = (x - mn_1 * mn_1) / dn;
             let an_1 = (a0 + mn_1) / dn_1;
 
-            v.push(an);
-
+            v[0] = an;
             // The convergence criteria „an_1 == 2 * a0“ is not good for
             // very small x thus I decided to break the iteration at constant
             // time. Which is the 10 below.
-            match v.len() {
-                10 => v,
-                _  => inner(v, x, a0, mn_1, dn_1, an_1),
+            if v.len() > 1 {
+                inner(&mut v[1..], x, a0, mn_1, dn_1, an_1);
             }
         }
 
-        Continuous(inner(Vec::new(), x, a0, 0, 1, a0))
+        let mut v :Vec<i64> = vec!(0; 10);
+        inner(&mut v, x, a0, 0, 1, a0);
+        Continuous(v)
     }
 }