Forum Discussion
List.Generate() takes only last element from IF statement?
I'm having trouble understanding why List.Generate() seems to take only the last element when an IF statement is used to generate next element. For example:
let
result = List.Generate( () =>
[listResult = null, nextOffset = 0, counter = 1],
each [counter] <= 2 ,
each [
listResult0 = {1,2},
listResult1 = {3,4},
listResult = if counter = 1 then listResult0 else listResult1,
counter = [counter] + 1],
each [listResult])
in
result
This returns a List of null (default element) and {3,4} as if dureing the first iteration the element {1,2} is not added to the list.
=> (expand)
Would anyone have an idea why the first element {1,2} is not added to the list?
Thanks,
Bartek
On the first iteration after the initialization, you have counter = [counter] + 1 = 1 + 1 = 2, so it returns listResult1. You probably want to write "if [counter] = 1" instead of "if counter = 1" since the latter is already incremented. Note that it doesn't matter if you write "counter = [counter] + 1" before or after listResult.
You may also want to start your counter at zero:
let result = List.Generate( () => [listResult = null, nextOffset = 0, counter = 0], each [counter] <= 2 , each [ listResult0 = {1,2}, listResult1 = {3,4}, listResult = if [counter] = 1 then listResult0 else listResult1, counter = [counter] + 1 ], each [listResult] ) in result
2 Replies
On the first iteration after the initialization, you have counter = [counter] + 1 = 1 + 1 = 2, so it returns listResult1. You probably want to write "if [counter] = 1" instead of "if counter = 1" since the latter is already incremented. Note that it doesn't matter if you write "counter = [counter] + 1" before or after listResult.
You may also want to start your counter at zero:
let result = List.Generate( () => [listResult = null, nextOffset = 0, counter = 0], each [counter] <= 2 , each [ listResult0 = {1,2}, listResult1 = {3,4}, listResult = if [counter] = 1 then listResult0 else listResult1, counter = [counter] + 1 ], each [listResult] ) in resultThanks, that explains! 🙂
