Advantages of Prolog

As I said above, Prolog is not a general-purpose theorem prover. It is a programming language in which procedures can be written as logical specifications. You have to know how it executes predicates in order to use it profitably.

Why use Prolog rather than C?

• It has built-in list handling, very useful for representing sequences, trees, and so on.

• It is easy to read and write programs which build structures.

  add( complex(A,B), complex(C,D),
       complex(E,F)
     ) :-
      E is A+C,
      F is B+D.

  Most Prologs nowadays should be able to handle structures of at least 30Kbytes in size.

• Although Prolog is not a complete implementation of logic, it is much closer to it than C, and is more like mathematical notation.

• It is easy to build tables and databases while a program is running, as I did with memo_fib. You don't need a lot of programming effort.

• You can reason about programs as algebraic objects. When writing a predicate, begin with a definition that is obviously correct, but inefficient. Then apply transformations that preserve its effect while making it more efficient. There is an example in replace.pl. See also The Craft of Prolog by Richard O'Keefe (MIT Press), and Essentials of Logic Programming by C.J.Hogger (Oxford University Press). I highly recommend O'Keefe.

  You can also use familiar methods of reasoning such as induction to prove that programs are correct. You may need to take the execution mechanism into account, but much less so than you would in C. See the proof in intervals.pl.