ln009 - X = b a b = X X = a b But a b = X no The Head-Tail...

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Prolog – Lists & Pattern Matching The unification operator: =/2 The expression A=B is true if A and B are terms and unify (look identical) arity ?- a = a. true ?- a = b. false ?- a = X. X = a ?- X = Y. true Read Sections 1&2 of Prolog Tutorial online NOTE: This is where Prolog really shines as an AI programming language: Knowledge representation - List Knowledge processing - pattern matching

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Prolog – Lists & Pattern Matching Lists – a convenient way to represent abstract concepts Prolog has a special notation for lists. [a] [a,b,c] [ ] Empty List [ bmw, vw, mercedes ] [ chicken, turkey, goose ]
Prolog – Lists & Pattern Matching Pattern Matching in Lists ?- [ a, b ] = [ a, X ].

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Unformatted text preview: X = b ?- [ a, b ] = X. X = [ a, b ] But: ?- [ a, b ] = [ X ]. no The Head-Tail Operator: [H|T] ?- [a,b,c] = [X|Y]; X = a Y = [b,c] ?- [a] = [Q|P]; Q = a P = [ ] Prolog – Lists The predicate first/2 : accept a list in the first argument and return the first element of the list in second argument. first(List,E) :- List = [H|T], E = H; Prolog – Lists The predicate last/2 : accept a list in the first argument and return the last element of the list in second argument. Recursion : there are always two parts to a recursive definition; the base and the recursive step . last([A],A). last([A|L],E) :- last(L,E)....
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