%%
database( {
	g(X:string,Y:string, C:integer)
} ).

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
export least_dist(X,Y,C).
export ld(X,Y,C).

%%
ld(X,Y,mmin<C>)<-g(X,Y,C).
ld(X,Y,mmin<C>)<-ld(X,Z,C1),ld(Z,Y,C2),C=C1+C2.
least_dist(X,Y,min<C>)<-ld(X,Y,C).

single(mmin, X, X).
multi(mmin,  X, Old, M) <- min(X,Old,M).
return(mmin, X, Old, M) <- min(X,Old,M).

min(X,nil,X).
min(X,Y,X)<-X<=Y.
min(X,Y,Y)<-Y<X.
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%