Prolog 运行长度编码

Question

由于我因病毒被困在家里无事可做，我决定开始学习 Prolog，我一直在解决学习 Prolog 和 99 个 Prolog 问题中的不同问题。

我目前遇到了一个运行长度编码问题，希望能提供有关该问题的任何帮助或指导。

这是我坚持的问题：

编写一个谓词 encode/2 ，它将未压缩列表作为第一个参数并返回压缩列表，如第二个参数所示。例如：

encode(['a','b','b','c','c','c','d','d'],X) should yield X = [ (a, 1), (b, 2), (c, 3), (d, 2)] .
encode(['a','p','p','l','e'],X) should yield X = [ (a, 1), (p, 2), (l, 1), (e, 1)] .```

And then to decode it:

Write a predicate decode/2 that takes the compressed list as a first parameter and returns the uncompressed list as shown as the second parameter. For example:
```decode([],X) should yield X = [].
decode([(a,1), (b,2), (c,3), (d,2)],X) should yield X = ['a','b','b','c','c','c','d','d'] .
decode([(a,1), (p,2), (l,1), (e,1)],X) should yield X =  ['a','p','p','l','e'].```

Answer 1

你可以从已有的开始：

encode(['a','b','b','c','c','c','d','d'], X) :-
    X = [ (a, 1), (b, 2), (c, 3), (d, 2) ] .

这意味着它也是这样的

encode(['b','b','c','c','c','d','d'], X2) :-
    X2 = [ (b, 2), (c, 3), (d, 2) ] .

因此

encode(['a','b','b','c','c','c','d','d'], X) :-
    encode(['b','b','c','c','c','d','d'], X2)
    X = [ (a, 1) | X2 ] .

与

相同

encode( L, X) :-
    L = ['a','b','b','c','c','c','d','d'],
    L = [ H | T ],
    encode( T, X2),
    X = [ (a, 1) | X2 ] .

与

相同

encode( L, X) :-
    L = ['a','b','b','c','c','c','d','d'],
    L = [ H | T ],
    encode( T, X2),
    add_encoded( H, X2, X).

add_encoded( 'a', [ (b, 2), (c, 3), (d, 2) ], X2 ) :-
    X2 = [ (a, 1) | [ (b, 2), (c, 3), (d, 2) ] ] .

你看到了吗？当我们通过用逻辑变量替换具体术语来概括我们的具体案例时，您是否看到代码是如何自己编写的？你还能继续这个吗？