Help required on Array appender

[Azi Hassan via Digitalmars-d-learn]

On Saturday, 2 September 2017 at 12:54:48 UTC, Nicholas Wilson 
wrote:

> If you're wanting to use appender just make an appender and 
> replace the ~= to calls to appender.put(data);

Just making Subdata an Appender!(string[][]) (or 
Appender!(Tuple!(string, string)[])) is enough since it already 
overloads the ~= operator.

Performance aside, a small nitpick is that it's possible to write 
filter!isFile instead of filter!(a => a.isFile) since isFile only 
accepts one argument.