| % generated: 17 November 1989 |
| % option(s): |
| % |
| % serialise |
| % |
| % David H. D. Warren |
| % |
| % itemize (pick a "serial number" for each |
| % unique integer in) a list of 25 integers |
| |
| serialise :- serialise("ABLE WAS I ERE I SAW ELBA",_). |
| |
| serialise(L,R) :- |
| pairlists(L,R,A), |
| arrange(A,T), |
| numbered(T,1,_). |
| |
| pairlists([X|L],[Y|R],[pair(X,Y)|A]) :- pairlists(L,R,A). |
| pairlists([],[],[]). |
| |
| arrange([X|L],tree(T1,X,T2)) :- |
| split(L,X,L1,L2), |
| arrange(L1,T1), |
| arrange(L2,T2). |
| arrange([],void). |
| |
| split([X|L],X,L1,L2) :- !, split(L,X,L1,L2). |
| split([X|L],Y,[X|L1],L2) :- before(X,Y), !, split(L,Y,L1,L2). |
| split([X|L],Y,L1,[X|L2]) :- before(Y,X), !, split(L,Y,L1,L2). |
| split([],_,[],[]). |
| |
| before(pair(X1,_),pair(X2,_)) :- X1 < X2. |
| |
| numbered(tree(T1,pair(_,N1),T2),N0,N) :- |
| numbered(T1,N0,N1), |
| N2 is N1+1, |
| numbered(T2,N2,N). |
| numbered(void,N,N). |
