Le 07/02/2015 02:48, Jeffrey Brown a écrit :

I see: what matters is that ++ has to traverse to the end of the first list. The order in which its two arguments are evaluated is irrelevant.

Thank you, David and Arjun!

On Fri, Feb 6, 2015 at 5:38 PM, Arjun Comar <nrujac@gmail.com> wrote:

Jeff,
An expression of the form xs ++ [x] appends the element to the end of the list. In order to evaluate the result, the ++ function iterates through the elements of the first list to find the end of the list then sets the tail of the last element of the first list to the second list.

Gentlemen, don't forget that Haskell is lazy, and this traversal takes place only when the list is effectively traversed by a consumer, which stores everything (and doesn't get rid of elements read). This might be the case here if somebody wants to keep and use the "digit representation" of a number, but please do not consider this phenomenon as inherent to the list creation algorithm.

Jerzy Karczmarczuk