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I am newbie to prolog and I am trying to flatten a list which is like this:

X = [[[0,0,1],[1,0,2]],[[0,1,3],[0,2,2]],[[0,3,5],[0,4,4]],[[0,5,4],[0,6,5]]]

The desired output is:

X = [[0,0,1],[1,0,2],[0,1,3],[0,2,2],[0,3,5],[0,4,4],[0,5,4],[0,6,5]]

How can I do this?

John Kugelman
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Josh
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1 Answers1

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Use recursion :-)

myflatten([], []).
myflatten([[A, B]|T], [A|[B|FlattenedT]]) :- myflatten(T, FlattenedT).

And then query:

?- myflatten([[[0,0,1],[1,0,2]],[[0,1,3],[0,2,2]],[[0,3,5],[0,4,4]],[[0,5,4],[0,6,5]]], X).

Evgeny
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  • Here is a simple rule of thumb: Whenever you see `|[` in a program, you can replace it by `,`. The second argument in the head of myflatten thus could read `[A,B|FlattenedT]` in place of `[A|[B|FlattenedT]]`. – false Jul 14 '11 at 00:02