%query: color_map(o,i). /* Sterling and Shapiro Program 14.4: Map coloring */ /* color_map(Map,Colors) :- Map is colored with Colors, so that no two neighbors have the same color. The map is represented as an adjacency-list of regions region(Name,Color,Neighbors), where Name is the name of the region, Color is its color, and Neighbors are the colors of the neighbors. */ color_map([Region|Regions],Colors) :- color_region(Region,Colors), color_map(Regions,Colors). color_map([],Colors). /* color_region(Region,Colors) :- Region and its neighbors are colored using Colors so that the regions color is different from the color of any of its neighbors. */ color_region(region(Name,Color,Neighbors),Colors) :- select(Color,Colors,Colors1), members(Neighbors,Colors1). select(X,[X|Xs],Xs). select(X,[Y|Ys],[Y|Zs]) :- select(X,Ys,Zs). members([X|Xs],Ys) :- member(X,Ys), members(Xs,Ys). members([],Ys). member(X,[X|_]). member(X,[_|Xs]) :- member(X,Xs). /* an example query ?- color_map( [ region(P,[E]), % portugal region(E,[F,P]), % spain region(F,[E,I,S,B,G,L]), % france region(B,[F,H,L,G]), % belgium region(H,[B,G]), % holland region(G,[F,A,S,H,B,L]), % germany region(L,[F,B,G]), % luxembourg region(I,[F,A,S]), % italy region(S,[F,I,A,G]), % switzerland region(A,[I,S,G]) % austria ], [red,yellow,blue,white]). */
content may be truncated. 'popout' for larger text window.
