Data science, ringifying & own blocks


I 'm using "Snap!" for data science. (BTW: Great feature. Thanks!) I 'm trying to build a "select 'columns' from 'table'" block - just for fun. Obviously, there is the "map" block for the same purpose.



If I ringify the input "columns", it 's working just fine.



If I do the ringifying in the block definition, I 'm getting an error output.

Where 's the difference? Is it a bug or is it a feature? Any help would be welcome. If you need to know more details, feel free to ask. Thank you in advance.

The second one first tries to get the second item from the empty slot (false). Because false is not a list, that cannot work. Then it tries to ringify that. The first one first makes a ring for getting the second item of a list and then passes it to map.

@spaceelephant Thanks for your immediate help. Now, it seems so obvious.

I was able to achieve my goal by doing it this way:

The input "columns" had to be a reporter.