Expand a list of various types into a new list

[shaunm001]

Trying to figure out how to programatically expand a list of various data types, including other lists. 

For example, here is a list of lists:

If I "drill down" to the next level using List.Combine, I now have more lists, and some text values:

The first List contained two Lists, the second List contained two text values.

Now I want to drill down again into those two list items, but I can't use List.Combine anymore, because that only works with data type List, and now I have some text values in my list. I want keep the text values as part of the new list, but continue drilling down into nested lists, until eventually I have a list of all text values. 

Any help would be greatly appreaciated! 

[shaunm001 · Accepted solution]

Thanks guys, I ended up using this function, works great!

[ziying35]

@shaunm001 

You want is similar to {{"a", "b"}, {"c", "d"}, "e", "f", {"g", {"h", "i"}}} to convert to {"a", "b", "c", "d", "e", "f", "g", "h", "i"}?

[AlB]

Hi @shaunm001 

try this, a recursive function that keeps using List.Combine until all lists have been expanded. For illustration purposes, it uses the list created in Source = and you'll see the result in the last step

let
  
  expandFunc_ = (inputList_)=>
  let
    step0 = List.Combine(List.Transform(inputList_, each if Value.Type(_) = type list then _ else {_})),
    step1 = List.Accumulate(inputList_, true, (state, current)=> state and Value.Type(current) <> type list  ),
    output = if step1 = true then step0 else @expandFunc_(step0) 
  in 
   output,  
  
  Source = {{"a", "b"}, {"c", "d"}, "e", "f", {"g", {"h", {"i",{"j", "l", "m"}}}}},
  resfunc = expandFunc_(Source)
in
  resfunc

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Cheers 

[Greg_Deckler]

Seems to me that you will need a new column where you make the decision to drill down or not based upon the data type. You could probably turn around and combine that into a single step in your M code.