Filter operator

[michaelko]

I'm suggesting a new operator ~. It takes two Arrays x and y, and return a Array [z| z=xi for all yi=true].

Example:
<[1,2,3,4,5] ~ [1,null,1,null]
>[1,3]

Or maybe a set?

<[1,2,3,4,5] ~ [1,null,1,null]
>1
>3

<[[1,2,3,4,5] ~ [1,null,1,null]]
>[1,3]

[stedolan]

I think this functionality is much too special-case to invent a new one-character operator for. I would like (and plan to implement) a zip function, so that you could zip together [1,2,3,4] and [1,null,1,null] to get [[1,1],[2,null],[3,1],[4,null]], which can be selected.