Turn a list into a matrix

Question

I worked all afternoon on a simple thing but cannot seem to get it right for some reason : how to turn a list into a matrix of given width.

Example : I got a list such a

Answer 1

You can divide the problem in two parts. The first building block would be to build a row of N elements. That is to take the input list and split it in two lists, one will have exactly N elements (the row) and the other is the remaining of the input list.

The second building block would be to build the matrix which is made of rows.

list_to_matrix([], _, []).
list_to_matrix(List, Size, [Row|Matrix]):-
  list_to_matrix_row(List, Size, Row, Tail),
  list_to_matrix(Tail, Size, Matrix).

list_to_matrix_row(Tail, 0, [], Tail).
list_to_matrix_row([Item|List], Size, [Item|Row], Tail):-
  NSize is Size-1,
  list_to_matrix_row(List, NSize, Row, Tail).