Question

I am trying to write a prolog program that can find the tiles that are completely surrounded by b or w in a 2D-array.

For example, given a dataset like this:

[
    [b, w, +, +],
    [w, +, w, b],
    [+, w, b, +],
    [+, +, +, b],
]

It would return another Variable containing:

[
    [-, -, -, -],
    [-, w, -, -],
    [-, -, -, b],
    [-, -, -, -],
]

That is, it replaced all the + which were completely surrounded with b with a b, and the same for those surrounded by a w, and replaced everything else with a -.

Can anyone give any ideas on how to build a program to do this?

Answer 1

This might help: it takes the representation you gave, and gives back a list whose elements are each of the form [ColumnIndex, RowIndex, Value]. You can then use member to find an element at a particular row/column.

encodearray( A, AA ) :- ( A, 0, 0, AA ).
encodearray( [], _, _, [] ).
encodearray( [[]|A], _, R, AA ) :- R1 is R+1, encodeArray( A, 0, R1, AA ).
encodearray( [[A|B]|X], C, R, [[C,R,A]|AA] ) :- C1 is C+1, encodeArray( [B|X], C1, R, AA ).