List Positions

[Dicken]

  Can some one explain what is happenign here so, straightforward  position;

[ alist = {1,3,2,"a",2,2,2,2,"a",2,2,2,2,"a",2,2} ,
result = List.PositionOf( alist, "a",Occurrence.All) ]

 but here I have a list of true / false   , the problem is Occurrence.All, if that is omitted then the first 'false is returned

otherwise an error. 

[ alist = {1,1,1,1,2,2,2,2,3,3,3,3,4,4,4,4,5,5,6,6,7},
tflist = List.Transform( List.Positions( alist),(x)=> alist{x} = alist {x+1} ) ,
result = List.PositionOf( tflist, false ,Occurrence.All ) ]

Richard

[slorin]

Hi @Dicken 

Another solution with List.IsDistinct

List.PositionOf(
   List.Transform(
       List.Zip({List.RemoveFirstN(alist,1), List.RemoveLastN(alist,1)}), 
       List.IsDistinct),
   true,
   Occurrence.All)

 Stéphane

[Dicken]

to answer my own question, the last value throws and error and this does not seem to liked by 
positons/ select etc; so I added a try otherwise and this solves the problem, there may be more elegant way ? 

let
    Source = [ alist = {1,1,1,1,2,2,2,2,3,3,3,3,4,4,4,4,5,5,6,6,7},
tflist = List.Transform( List.Positions( alist),(x)=>  
try alist{x} = alist {x+1} otherwise   true ) ],
    Custom1 = List.PositionOf(   Source [tflist], 
false , Occurrence.All)
in
    Custom1

[p45cal · Accepted solution]

There's guaranteed to be an error in the last member of the list (you're referring to x+1 which doesn't exist).

Using an otherwise = true will mask that error which is fine, although as a coder you'll realise this masks any other error that may appear in the list and you wouldn't be alerted to it. My approach would be to remove the known error at the end of the list with a List.RemoveLastN(tflist,1) (or do it in the same line) so that you're only removing the expected error, then do your ListPositionOf with Occurence.All.

[Dicken]

Thank you both. 

[MasonMA]

I think your try/otherwise approach is perfectly valid and likely the most maintainable option:)