protected void onPrepareResult() {
        if (args.size() == 1) {
            setResult(ArithmeticTypeConversion.getType(args.get(0).getResult()));
        } else if (args.size() > 1) {
            setResult((ResultNode)args.get(0).getResult().clone());
            for (int i = 1; i < args.size(); i++) {
                if (args.get(i).getResult() != null) {
                    setResult(ArithmeticTypeConversion.getType(getResult(), args.get(i).getResult()));
                }
            }
        }
    }
<p>Perform the appropriate calculation of the arguments into a result node.</p>

@param args   A list of operands.
@param result Place to put the result.
@return True if successful, false if not.
searchlib/src/main/java/com/yahoo/searchlib/expression/MultiArgFunctionNode.java