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POFind all paths between point on board
 

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    <p>In this topic: <a href="https://stackoverflow.com/questions/17170517/how-find-path-at-the-m-x-n-table/17222618#17222618">How find path at the m x n table</a> I found out how generate paths between two points, and this is code:</p> <pre><code>go m n (i,j) = [ (i+1,j) | i&lt;m ] ++ [ (i-1,j) | i&gt;1 ] ++ [ (i,j+1) | j&lt;n ] ++ [ (i,j-1) | j&gt;1 ] -- isEndOfPath p q = (p == q) genPath p q acc m n input buf = g p q acc buf where g p q acc buf | p==q = [(acc)] -- return acc, buf g p q acc buf = [s | r &lt;- go m n q, notElem r buf, notElem r acc, notElem r input, s &lt;- genPath p r (r:acc) m n input (r:buf)] ++ [s | r &lt;- go m n q, notElem r acc, r==p, s &lt;- genPath p r (r:acc) m n input (r:buf)] </code></pre> <p>For example, we can search path from (2,2) to (1,1) on board 2x2. Thus, we can call it as </p> <pre><code>genPath (2,2) (1,1) [(1,1)] 2 2 [(3,3),(1,1)] [(1,1)] </code></pre> <p>and we have result</p> <pre><code>[[(2,2),(2,1),(1,1)],[(2,2),(2,1),(1,1)],[(2,2),(1,2),(1,1)],[(2,2),(1,2),(1,1)]] </code></pre> <p>So we have correct paths.</p> <p>And now i will find all paths between pairs of points. In Prolog it was very easy and I haven't any problem with this. So, mayby I show you my algorithm and code:</p> <p>First predicat - when we find all paths, we return it:</p> <pre><code>genAllPaths([],A,A,_,_,_,_). </code></pre> <p>Else, we must generate paths recursively. So, firs we find path between first pairs, and then we can search other paths:</p> <pre><code>genAllPaths([(I1,J1),(I2,J2)|T],Acc,S,M,N,Input,Bufor) :- genPath((I1,J1),(I2,J2),[(I2,J2)],X,M,N,Input,[(I2,J2)|Bufor],NewBufor), genAllPaths(T,[X|Acc],S,M,N,Input,NewBufor). </code></pre> <p>If you don't understand something, please ask me. </p> <p>Hence, now I'll do it in haskell. I tried, but again, I have a lot of problems with it. If you know how do it and would like help me - I will very grateful.</p>
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    1. COStackOverflow doesn't work as well for this style of question. I suggest you try to go somewhere more interactive with it like the #haskell IRC channel (on freenode). I think you'll get better help there.
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      1. USTikhon Jelvis
    2. COI agree with Tikhon Jelvis. "Hence, now I'll do it in haskell. I tried, but again, I have a lot of problems with it. If you know how do it and would like help me - I will very grateful." <- This is probably too general of a question. It would be better to ask about a specific/narrow barrier/problem you are trying to over come.
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    3. COyou have 8 arguments in the call to `genPath/9`. `S` is passed around unchanged. Please recheck your Prolog code.
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      1. USWill Ness
 

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