Golfer-Riddle (Prolog-Version)

In my ongoing quest for improved awareness for rule-based systems, I solved the golfer-riddle in Prolog and published the solution together with an explanation here.

It's a pretty straightforward translation of the riddle itself - Prolog rocks!
(I'm open to improvisation suggestions...)

gcolor(blue).
gcolor(plaid).
gcolor(orange).
gcolor(red).

gpos(1).
gpos(2).
gpos(3).
gpos(4).

golfer( [_, C, P] ) :- gcolor(C), gpos(P).
		
golferRiddle( G1, G2, G3, G4) :-  golfer(G1),golfer(G2),golfer(G3), golfer( G4),
	G1 = [fred, FredCol, FredPos ], 
	G2 = [joe, JoeCol, 2],
	G3 = [tom, TomCol, TomPos], 
	TomPos =\= 1, TomPos =\= 4,
	TomCol \= orange,
	G4 = [bob, plaid, BobPos],
	
	/* unique colors */
	is_set([FredCol, JoeCol, TomCol, plaid]),
	
	/* unique positions */ 
	is_set([FredPos, TomPos, BobPos, 2]), 
	 
	/* Fred's right neighbour wears blue */
        plus( FredPos, 1, FP1),
        member( [_, blue, FP1], [G1, G2, G3, G4]).