roundrobin needs a metaoperator

[lizmat]

This seems obvious, but I did not see another issue relating to it.

zip's infix and metaoperator, Z is tremendously valuable, but it is extremely common to run up against the need to drop down to using roundrobin because the input does not contain equally sized lists. One such example came up today on reddit here:

https://old.reddit.com/r/perl6/comments/c2hw1u/some_code_golf_help_requested/erkzbh1/

The obvious approach in that case would be to reverse the lists of digits, roundrobin add them and then re-join them in a single number.

Assuming we had a roundrobin infix and metaoperator ➿, this would change the code:

+ [~] [Zmax] context-pad(@nums).map: {.comb }

to:

+ flip [~] [➿max] @nums.map: {.flip.comb }

Which isn't simply code-golfing, but actually obviates the need for the context-pad step that zero-pads all of the input numbers.

Expected Behavior

zip and roundrobin are equal peers.

Actual Behavior

They are not.