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POProlog: how to do "check(a++b++c++d equals d++a++c++b) -> yes"
 

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  1. POProlog: how to do "check(a++b++c++d equals d++a++c++b) -> yes"
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    <p>Let's define custom operators - let it be <code>++</code>,<code>equals</code></p> <pre><code>:- op(900, yfx, equals). :- op(800, xfy, ++). </code></pre> <p>And fact:</p> <pre><code>check(A equals A). </code></pre> <p>I try to make predicate, let it be <code>check/1</code>, that will return true in all following situations:</p> <pre><code>check( a ++ b ++ c ++ d equals c ++ d ++ b ++ a ), check( a ++ b ++ c ++ d equals d ++ a ++ c ++ b), check( a ++ b ++ c ++ d equals d ++ b ++ c ++ a ), % and all permutations... of any amount of atoms check( a ++ ( b ++ c ) equals (c ++ a) ++ b), % be resistant to any type of parentheses </code></pre> <p>return</p> <pre><code>yes </code></pre> <p><strong>How to implement this in Prolog?</strong> (Code snippet, please. Is it possible? Am I missing something?)</p> <p>Gnu-Prolog is preferred, but SWI-Prolog is acceptable as well.</p> <p>P.S. Please treat code, as draft "pseudocode", and don't care for small syntax issues.</p> <p>P.P.S '++' is just beginning. I'd like to add more operators. That's why I'm afraid that putting stuff into list might be not good solution.</p> <h3>Additionally</h3> <p>Additionally, would be nice, if queries would be possible (but, this part <strong>is not required</strong>, if you are able to answer to first part, it's great and enough)</p> <pre><code>check( a ++ (b ++ X) equals (c ++ Y) ++ b) ) </code></pre> <p>one of possible results (thanks @mat for showing others)</p> <pre><code>X=c, Y=a </code></pre> <p>I am looking mostly for solution for first part of question - "yes/no" checking.</p> <p>Second part with X,Y would be nice addition. In it X,Y should be simple atoms. For above example domains for X,Y are specified: <code>domain(X,[a,b,c]),domain(Y,[a,b,c])</code>.</p>
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    1. USGrzegorz Wierzowiecki
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      1. POProlog: how to do "check(a++b++c++d equals d++a++c++b) -> yes"
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      1. VTUpMod
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      1. POProlog: how to do "check(a++b++c++d equals d++a++c++b) -> yes"
      1. USGrzegorz Wierzowiecki
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      1. POProlog: how to do "check(a++b++c++d equals d++a++c++b) -> yes"
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    1. COHi, you know you can "accept" answers by clicking the big checkmark, right?
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      1. POProlog: how to do "check(a++b++c++d equals d++a++c++b) -> yes"
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    2. COYes, I know :).
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      1. POProlog: how to do "check(a++b++c++d equals d++a++c++b) -> yes"
      1. USGrzegorz Wierzowiecki
    3. COI would not use ++, this is often found for string concatenation. But string concatenation is not commutative. But what you show here by permutation is an effect of commutativity and associativity.
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      1. POProlog: how to do "check(a++b++c++d equals d++a++c++b) -> yes"
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