Re: Exposing Perl programmers to logic programming

On 8 Mar 2005, at 19:18, Ovid wrote:
[snip]
My question in a nutshell:  given 45 minutes to show a roomful of
programmers with no prior experience in logic programming just how
powerful it can be, what approach would you take?
[snip]

I've used this little example to impress people (shamelessly stolen 
from <http://www.ainewsletter.com/newsletters/aix_0305.htm>.)

Start off with

	member( X, [ X | _ ] ).
	member( X, [ _ | Z ] ) :- member( X, Z ).

which is enough to demonstrate the declarative and generative stuff you 
can get out of simple statements, then hit them with:

	send( Object, Message ) :-
		class( Object, methods( Methods ) ),
		member( ( Message :- Method ), Methods ),
		call( Method ).

	class(
         rectangle( H, W ),
         methods( [
             ( area(A) :- A is H * W ),
             ( perimeter(P) :- P is 2 * (H + W) )
         ] )
     ).
	
	class(
         circle(R),
         methods( [
             ( area(A) :- A is pi * R * R ),
             ( perimeter(P) :- 2 * pi * R )
         ] )
     ).

allowing us to do:

     ?- send( circle(1), area(A) ).
     A = 3.14159

Implementing a basic OO system in 6 lines of code is kinda neat :-)

Cheers,

Adrian