simple chain is join of iterables
how get something like this
for m=[[1,2],[3,4,5,6],[7,8,9],[10,11,12,13,14]] return [1,2,5,6,14] ?
cose:
<code>[1,2]
[_,_,5,6]
[_,_,_]
[_,_,_,_,14]
</code>
<code>[1,2]
[_,_,5,6]
[_,_,_]
[_,_,_,_,14]
</code>
[1,2]
[_,_,5,6]
[_,_,_]
[_,_,_,_,14]