Optimize pow3 and pow4 (#963)

Author: lynn

src/compile/optimize.rs

@@ -123,8 +123,10 @@ static UNSORTED_OPTS: &[&dyn Optimization] = &[
     &((Sort, Last), LastSort),
     &((Pop, Rand), ReplaceRand),
     &((Pop, Pop, Rand), ReplaceRand2),
-    &((-1, Pow), (1, Flip, Div)),
+    &((-1, Pow), Reciprocal),
     &((2, Pow), (Dup, Mul)),
+    &((3, Pow), (Dup, Dup, Mul, Mul)),
+    &((4, Pow), (Dup, Mul, Dup, Mul)),
     &((Complex, Abs), AbsComplex),
     &((Abs, Dup, Mul), (SquareAbs)),
     &ByToDup,

src/value.rs

@@ -1880,9 +1880,21 @@ impl Value {
     pub fn pow(self, base: Self, env: &Uiua) -> UiuaResult<Self> {
         if let Ok(pow) = self.as_int(env, None) {
             match pow {
+                -1 => return base.div(Value::from(1), env),
                 1 => return Ok(base),
                 2 => return base.clone().mul(base, env),
-                -1 => return base.div(Value::from(1), env),
+                3 => {
+                    return base
+                        .clone()
+                        .mul(base.clone(), env)
+                        .and_then(|square| square.mul(base, env));
+                }
+                4 => {
+                    return base
+                        .clone()
+                        .mul(base, env)
+                        .and_then(|square| square.clone().mul(square, env));
+                }
                 _ => {}
             }
         }