Question

我开始使用prolog几个星期了，然而我却更深入地看到了操纵列表的递归谓词的构造。我的问题是：它可以构建一个谓词，在给定数量的其他列表中拆分给定列表吗？

例如，我想象的那样：

split([H|T], NumberLists, Lists) - 递归实现 -

?- split([1,2,3,4,5,6,7,8],2,Lists).
Lists = [[1,2,3,4],[5,6,7,8]].

?- split([1,2,3,4,5,6,7,8],4,Lists).
Lists = [[1,2],[3,4],[5,6],[7,8]].

有人能给我一个实施的例子吗？

谢谢！

Answer 1

这样的事应该做。没有内置谓词：

partition( [] , _ , []       ) .  % the empty list is already partitioned
partition( Xs , N , [Pfx|Ys] ) :- % for a non-empty list, we...
  take(N,Xs, Pfx , Sfx ) ,        % - split it into a prefix of (at most) length N and its suffix.
  partition(Sfx,N,Ys)             % - recursively partition the suffix
  .                               % Easy!

take( 0 , Xs  , []     , Xs  ) .     % if we reach zero, we're done. Close the prefix and hand back whatever is left over.
take( N , []  , []     , []  ) :-    % if we exhaust the source list, we're done. close the prefix and hand back the empty list as the suffix.
  N > 0                              % - assuming, of course, that N is greater than zero.
  .                                  %
take( N , [X|Xs] , [X|Ys] , Sfx ) :- % otherwise prepend the current item to the prefix
  N > 0 ,                            % - assuming N is greater than zero,
  N1 is N-1 ,                        % - then decrement N
  take(N1,Xs,Ys,Sfx)                 % - and recurse down.
  .                                  % Also easy!

在Prolog中动态拆分列表

1 个答案: