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How to write a Prolog program

How to write a Prolog program. Design data structures to represent input, output and intermediary data as required

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How to write a Prolog program

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  1. Simply Logical – Chapter 3 How to write a Prolog program

  2. Simply Logical – Chapter 3 • Design data structures to represent input, output and intermediary data as required • Design algorithms to perform the task using only 2 forms of control: selection and recursion. The algorithm is developed ina hierarchicaltop-down mannerand terminates when all subtasks are elementary. • Translate the algorithms form the step 2 into Prolog programs. • Check correctness of programs by checking correctness of each procedure (testing is carried out bottom-up). • Add comments specifying a typical query to the program.

  3. Simply Logical – Chapter 3 p.74-6 • Write down declarative specification of partition • % partition(L,N,Littles,Bigs) <- Littles contains numbers • % in L smaller than N, • % Bigs contains the rest • Identify recursion and ‘output’ arguments • Write down skeleton • partition([],N,[],[]). • partition([Head|Tail],N,?Littles,?Bigs):-/* do something with Head */partition(Tail,N,Littles,Bigs). Logic programming methodology

  4. Simply Logical – Chapter 3 p.74-6 • Complete bodies • partition([],N,[],[]). • partition([Head|Tail],N,?Littles,?Bigs):-Head < N,partition(Tail,N,Littles,Bigs),?Littles = [Head|Littles],?Bigs = Bigs. • partition([Head|Tail],N,?Littles,?Bigs):-Head >= N,partition(Tail,N,Littles,Bigs),?Littles = Littles,?Bigs = [Head|Bigs]. • Fill in ‘output’ arguments • partition([],N,[],[]). • partition([Head|Tail],N,[Head|Littles],Bigs):-Head < N,partition(Tail,N,Littles,Bigs). • partition([Head|Tail],N,Littles,[Head|Bigs]):-Head >= N,partition(Tail,N,Littles,Bigs). Methodology

  5. Simply Logical – Chapter 3 p.76 • Write down declarative specification for sorting • % sort(L,S) <- S is a sorted permutation of list L • Write down skeleton • sort([],[]). • sort([Head|Tail],?Sorted):-/* do something with Head */sort(Tail,Sorted). • Complete body (auxiliary predicate needed) • sort([],[]). • sort([Head|Tail],WholeSorted):-sort(Tail,Sorted),insert(Head,Sorted,WholeSorted). Writing a sort predicate

  6. Simply Logical – Chapter 3 p.77 • Write down declarative specification • % insert(X,In,Out) <- In is a sorted list,e.g.[2,4,7,9] • % Out is In with X inserted in the proper place • % ?- insert(5,[2,4,7,9],Out). Out=[2,4,5,7,9] • Write down skeleton • insert(X,[],?Inserted). • insert(X,[Head|Tail],?Inserted):-/* do something with Head */insert(X,Tail,Inserted). Writing an insert predicate

  7. Simply Logical – Chapter 3 p.77 • Complete bodies • insert(X,[],?Inserted):-?Inserted=[X]. • insert(X,[Head|Tail],?Inserted):-X > Head,insert(X,Tail,Inserted),?Inserted = [Head|Inserted]. • insert(X,[Head|Tail],?Inserted):-X =< Head,?Inserted = [X,Head|Tail]. • Fill in ‘output’ arguments • insert(X,[],[X]). • insert(X,[Head|Tail],[X,Head|Tail]):-X =< Head. • insert(X,[Head|Tail],[Head|Inserted]):-X > Head,insert(X,Tail,Inserted). Writing an insert predicate

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