topic Re: Nested Lists in Discussions

Nested Lists

SpannerHead — Tue, 01 Apr 2025 21:24:07 GMT

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}

Re: Nested Lists

mmarchandFSLR — Tue, 01 Apr 2025 21:32:38 GMT

Here's one way, assuming the items inside the outer list are all lists. If they might not be, you just need to add a little more code to handle it.

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

Re: Nested Lists

txnelson — Tue, 01 Apr 2025 21:34:27 GMT

You just need to concatenate the individual lists;

Names Default To Here( 1 );
l1 = {{:A, :B, :C}, {:D, :E, :F}};

l2 = l1[1] || l1[2];

I suggest you take the time to read the section of the Scripting Guide on the creation and manipulation of Lists.

Re: Nested Lists

SpannerHead — Tue, 01 Apr 2025 22:11:32 GMT

Had to tweak this. Works now. Thanks.

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

Re: Nested Lists

mmarchandFSLR — Wed, 02 Apr 2025 12:21:31 GMT

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}

Re: Nested Lists

pmroz — Thu, 03 Apr 2025 15:24:11 GMT

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}