Re: Flatten, question

Use append(FlatHead, FlatTail, List) instead of concat(...).

concat/3 is for combining atoms to create a new atom. append/3 is for  
appending lists to create a new list: more generally it is true if the  
third argument is the list that is the second argument list appended  
to the first argument list.

Lindsey

On Oct 30, 2008, at 2:13 PM, Hartmut Lange wrote:

> Everybody,
> is somebody here who can help me in this small algorithm.
> Why do I get
>  atom_concat/3: Type error: `atomic' expected, found `[g]'
>  atom_concat/3: Type error: `atomic' expected, found `[e]'
> in the line where flatten1(...) is called with the list of a,b,c...
> What's wrong with that... hmm? I found it in the Prolog book of  
> Bratko, excercise 3.11
> I am using SWI-Prolog 5.6
> Regards,
>
>
> flatten1([Head|Tail], List) :-
>    flatten1(Head, FlatHead),
>    flatten1(Tail, FlatTail),
>    concat(FlatHead,FlatTail, List).
>
> flatten1([], []).
> flatten1(X, [X]).
>
> :- flatten1([a,b,c,e,f,g], List),
>   write('Flat List:'), write(List).
>
> :- flatten1([a,b,[c,e],f,g], List),
>   write('Flat List:'), write(List).
>
>
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