Re: against list flattening

"Richard A. O'Keefe" <[email protected]> writes:

> The clincher, of course, is
>
> 	L = [a,B,c], flatten(L, R), B = [2,3]
> =>	R = [a.[2,3],c]
>
> which is not flat.

I would like to endorse this excellent argument. flatten/2 does not
satisfy important declarative properties exactly because variables that
occur in its first argument are implicitly considered to be non-lists,
although declaratively, they stand for lists as well. In many cases,
append/*2*, which has much nicer properties, perfectly suffices.