[GitHub] [commons-math] aherbert commented on a diff in pull request #225: Avoid duplicate code.

[GitBox <gi...@apache.org>]

aherbert commented on code in PR #225:
URL: https://github.com/apache/commons-math/pull/225#discussion_r1002386033


##########
commons-math-legacy/src/main/java/org/apache/commons/math4/legacy/ode/nonstiff/HighamHall54StepInterpolator.java:
##########
@@ -100,9 +103,9 @@ protected void computeInterpolatedStateAndDerivatives(final double theta,
     } else {
         final double theta2 = theta * theta;
         final double b0 = h * (-1.0/12.0 + theta * (1.0 + theta * (-15.0/4.0 + theta * (16.0/3.0 + theta * -5.0/2.0))));
-        final double b2 = h * (-27.0/32.0 + theta2 * (459.0/32.0 + theta * (-243.0/8.0 + theta * 135.0/8.0)));
-        final double b3 = h * (4.0/3.0 + theta2 * (-22.0 + theta * (152.0/3.0  + theta * -30.0)));
-        final double b4 = h * (-125.0/96.0 + theta2 * (375.0/32.0 + theta * (-625.0/24.0 + theta * 125.0/8.0)));
+        final double b2 = h * (-27.0/32.0 + theta2 * v);

Review Comment:
   I do not mind the duplicate code. I am assuming this has been written based on a known method for the 5(4) Higham and Hall integrator and would be recognisable when compared to the original source.
   
   However it can be improved with better formatting within the else block:
   ```Java
   final double b0 = h * (-1.0/12.0   + theta  * (1.0        + theta * (-15.0/4.0   + theta * (16.0/3.0 + theta * -5.0/2.0))));
   final double b2 = h * (-27.0/32.0  + theta2 * (459.0/32.0 + theta * (-243.0/8.0  + theta * 135.0/8.0)));
   final double b3 = h * (4.0/3.0     + theta2 * (-22.0      + theta * (152.0/3.0   + theta * -30.0)));
   final double b4 = h * (-125.0/96.0 + theta2 * (375.0/32.0 + theta * (-625.0/24.0 + theta * 125.0/8.0)));
   final double b5 = h * (-5.0/48.0   + theta2 * (-5.0/16.0  + theta *  5.0/12.0));
   ```



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