zoomInterpolate.rho() has no getter

ref #61 (comment)

README.md

@@ -131,9 +131,9 @@ Returns an interpolator between the two views *a* and *b* of a two-dimensional p
 
 The returned interpolator exposes a *duration* property which encodes the recommended transition duration in milliseconds. This duration is based on the path length of the curved trajectory through *x,y* space. If you want a slower or faster transition, multiply this by an arbitrary scale factor (<i>V</i> as described in the original paper).
 
-<a name="interpolate_rho" href="#interpolate_rho">#</a> *interpolateZoom*.<b>rho</b>(<i>[rho]</i>) · [Source](https://github.com/d3/d3-interpolate/blob/master/src/zoom.js)<!-- , [Examples](https://observablehq.com/@d3/interpolatezoom-rho) -->
+<a name="interpolate_rho" href="#interpolate_rho">#</a> *interpolateZoom*.<b>rho</b>(<i>rho</i>) · [Source](https://github.com/d3/d3-interpolate/blob/master/src/zoom.js)<!-- , [Examples](https://observablehq.com/@d3/interpolatezoom-rho) -->
 
-Given a [zoom interpolator](#interpolateZoom), returns a new zoom interpolator using the specified curvature *rho*. When *rho* is close to 0, the interpolator is almost linear. The default curvature is sqrt(2). If *rho* is not specified, returns the interpolator’s curvature.
+Given a [zoom interpolator](#interpolateZoom), returns a new zoom interpolator using the specified curvature *rho*. When *rho* is close to 0, the interpolator is almost linear. The default curvature is sqrt(2).
 
 <a name="interpolateDiscrete" href="#interpolateDiscrete">#</a> d3.<b>interpolateDiscrete</b>(<i>values</i>) · [Source](https://github.com/d3/d3-interpolate/blob/master/src/discrete.js), [Examples](https://observablehq.com/@d3/d3-interpolatediscrete)
 

src/zoom.js

@@ -63,7 +63,6 @@ export default (function zoomRho(rho, rho2, rho4) {
   }
 
   zoom.rho = function(_) {
-    if (arguments.length === 0) return rho;
     var _1 = Math.max(1e-3, +_), _2 = _1 * _1, _4 = _2 * _2;
     return zoomRho(_1, _2, _4);
   };

test/zoom-test.js

@@ -15,10 +15,9 @@ tape("interpolateZoom returns the expected duration", function(test) {
 
 tape("interpolateZoom parameter rho() defaults to sqrt(2)", function(test) {
   test.inDelta(
+    interpolate.interpolateZoom([0,0,1], [10, 10, 5])(0.5),
     interpolate.interpolateZoom.rho(Math.sqrt(2))([0,0,1], [10, 10, 5])(0.5),
-    interpolate.interpolateZoom([0,0,1], [10, 10, 5])(0.5)
   );
-  test.inDelta(interpolate.interpolateZoom.rho(), Math.sqrt(2));
   test.end();
 });