Nested Lists

Question

I have somehow generated a nested list of columns due to them having been initially grouped.  I would like to remove the nesting to have a continuous list of columns I can act on.

Instead of {{:A, :B, :C}, (:D, :E, :F}}, I would like to get to {:A, :B, :C, :D , :E, :F}

pmroz · Answer

Building on Jim's solution.  If you have more than two sublists:

Names Default To Here( 1 );
l1 = {{:A, :B, :C}, {:D, :E, :F}, {:G, :H, :I, :J}};
l3 = {};
for (i = 1, i <= nitems(l1), i++,
	insertinto(l3, l1[i]);
);
print(l3);

{:A, :B, :C, :D , :E, :F, :G, :H, :I, :J}

mmarchandFSLR · Answer

Ah, sorry.  I was testing on strings, and I forgot that inserting a list into a list actually inserts the unevaluated items of the list.  If you have any columns that are not inside of a nested list, they will be inserted as missing, for example:

Names Default To Here( 1 );
this_list = {{:A, :B, :C}, :D, {:E, :F, :G}};
new_list = {};
For Each( {v, i}, this_list, Insert Into( new_list, v ) );

//{:A, :B, :C, ., :E, :F, :G}

You can solve the issue by using Name Expr():

Names Default To Here( 1 );
this_list = {{:A, :B, :C}, :D, {:E, :F, :G}};
new_list = {};
For Each( {v, i}, this_list, Insert Into( new_list, Name Expr( v ) ) );

//{:A, :B, :C, :D, :E, :F, :G}

SpannerHead · Answer

Had to tweak this.  Works now.  Thanks.

For Each( {val, idx}, this_list,
		Insert Into( new_list, val )
);