Flattening lists
We 'flatten' a list by removing all the square brackets around
any lists it contains as elements, and around any lists that its
elements contain as elements, and so on for all nested
lists. For example, when we flatten the list
[a,b,[c,d],[[1,2]],foo] we get the list
[a,b,c,d,1,2,foo] and when we flatten the list
[a,b,[[[[[[[c,d]]]]]]],[[1,2]],foo,[]] we also get
[a,b,c,d,1,2,foo].
Write a predicate my_flatten(+List,?Flat) (you
cannot use the name flatten because it is already
defined in Prolog) that holds when the first argument
List flattens to the second argument
Flat. There are many ways of writing this
predicate. For the moment, try to come up with one using
append (the built-in version of
concatenate). We will discuss a more elegant one
which is not making use of append in the exercise about
accumulators.