[Complex] add polar; fix "returns" traits

Author: moritz

lib/Complex.pod

@@ -17,27 +17,34 @@ Adding a trailing C<i> to a number literal makes it a Complex, for example
 
 =head2 new
 
-    proto method new(*@, *%) {*}
-    multi method new(Real $re, Real $im)
+    proto method new(*@, *%) {*} returns Complex:D
+    multi method new(Real $re, Real $im) returns Complex:D
 
 Creates a new C<Complex> object from a the real and imaginary part.
 
 =head2 re
 
-    method re(Complex:D:) return Real:D
+    method re(Complex:D:) returns Real:D
 
 Returns the real part of the complex number
 
 =head2 im
 
-    method im(Complex:D:) return Real:D
+    method im(Complex:D:) returns Real:D
 
 Returns the imaginary part of the complex number
 
 =head2 isNaN
 
-    method isNaN(Complex:D:) return Bool:D
+    method isNaN(Complex:D:) returns Bool:D
 
 Returns true if the real or imaginary part is C<NaN> (not a number)
 
+=head2 polar
+
+    method polar(Complex:D:) returns Positional:D
+
+Returns a two-element list of the polar coordinates for this value,
+ie magnitude and angle in radians.
+
 =end pod