Fix some edges on Fractional handling

fractional/src/fractional.rs

@@ -129,7 +129,11 @@ impl Fractional {
                 }
             }
 
-            inner(1, x / 2, x)
+            match x {
+                0 => 0.into(),
+                1 => 1.into(),
+                _ => inner(1, x / 2, x),
+            }
         }
 
         let Fractional(n, d) = self;
@@ -141,7 +145,7 @@ impl Fractional {
         };
 
         let d = match d.cmp(&0) {
-            Ordering::Equal   => return Err("division by zero"),
+            Ordering::Equal   => 0.into(),
             Ordering::Less    => return Err("sqrt on negative undefined"),
             Ordering::Greater => floor_sqrt(d),
         };
@@ -268,10 +272,7 @@ impl Sub for Fractional {
     type Output = Self;
 
     fn sub(self, other: Self) -> Self {
-        let Fractional(n1, d1) = self;
-        let Fractional(n2, d2) = other;
-        let n = n1 * (self.gcd(other) / d1) - n2 * (self.gcd(other) / d2);
-        Self(n, self.gcd(other)).reduce()
+        self + -other
     }
 }