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POProlog shortcut to creating a custom enumeration
 

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    <p>I am trying to create a custom enumeration via a series of facts.</p> <pre> greater(X,Y) :- less (Y,X). less(a,b). less(b,c). less(c,d). </pre> <p>This works fine, however there is significant repetition.</p> <p>I'm trying to cut that down. Is there a way to use an array for a simple linear series of facts via a transformation?</p> <pre> transform([a,b,c,d]) resulting in the same less definitions. </pre> <p>I have already created a "less" definition that uses an array and the nextto/member function to test, however I cannot add exceptions or equivalent cases like I could with individual declarations. Hence my interest in shortcutting the simple case definition, and then the desire to supplement it with more definitions.</p> <p>This reminds me of where defmacro in lisp is useful.</p> <p>Thanks.</p> <p><strong>Edit:</strong></p> <p>I was able to generate one series using assert. It successfully defines everything, but returns an error. I get the impression this isn't the correct method.</p> <pre> set_less([]). set_less([X,Y|L]):- assert( myless(X,Y) ) , set_less([Y|L]). :- set_less([a,b,c,d]). Output: Goal (directive) failed: user:set_less([a, b, c, d]) ?- listing. :- dynamic myless/2. myless(a, b). myless(b, c). myless(c, d). </pre> <p><strong>Second Edit:</strong></p> <pre> mylist([a,b,c,d]). set_less([]). set_less([_]). ----- Key! set_less([X,Y|L]):- assert( myless(X,Y) ) , set_less([Y|L]). :- set_less([a,b,c,d]). </pre> <p>That does work! Is this a good way to define custom enumerations? I see it works now, thanks!</p>
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    1. CO@demosthenex: Your set_less/1 predicate could be made to work. Trace the goal set_less([a,b,c,d]), and you'll find that it fails because set_less([d]) fails.
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