I want to check for an element in a nested list.
I already tried several ways but I will always get the wrong result or some errors.
[X] `elem` [[X,X,X],[O,O,O]]
returns False but should be True
X `elem` [[X,X,X],[O,O,O]]
throws a error, that types can not be matched.
Do I miss something here?
The elements of the list are sublists, and there is no [X] sublist in the list.
You can check if any of the elements of the sublists contain X with:
any (elem X) [[X, X, X], [O, O, O]]or with elem as infix operator:
any (X `elem`) [[X, X, X], [O, O, O]]but these are semantically completely identical.
These will check if for any of the sublists (here [X, X, X] and [O, O, O]), X is an element of these lists.
Another option, as @amalloy described is to concatenate all the sublists into a list, and then perform an elem check on these, so:
elem X (concat [[X, X, X], [O, O, O]])