Question

我正在尝试在lisp中定义A *搜索算法

可以找到伪代码here。

这是我到目前为止所做的：

;;; A*
(defun a* (problem)
;;;;;;;;;;;;;;;;;;;;;;;;;;;  cameFrom -> Parent do node 
;;;;;;;;;;;;;;;;;;;;;;;;;;;  gScore   -> node-g
;;;;;;;;;;;;;;;;;;;;;;;;;;;  fScore   -> node-g  +  node-h        
    (setq closedSet '())
    (setq openSet (list (make-node :state (problem-initial-state problem))))
    (setq listaVizinhos '())

    (loop while(not(eq openSet nil))  

        (setq tamanho_openS (list-length (openSet)))                                                            ;                            
        (setq current (nth 0 openSet))                                                                          ; 
        (dotimes (i tamanho_openS)                                                                              ;PARA ENCONTRAR O NODE COM MENOR FSCORE
            (if (< (+ (node-g (nth i openSet)) (node-h (nth i openSet)))  (+ (node-g current) (node-h current)))  ;                CURRENT
            (setq current (nth i openSet))))                                                                    ;

        (if (funcall (problem-fn-isGoal problem) (node-state current)) (return-from a* (solucao current)))      ; caso current seja solucao -> retorna-o para a funcao solucao (que cria a solucao pedida)

        (remove current openSet) ; retira o curretn da lista dos abertos
        (append (list(current)) closedSet) ; introduz curretn na lista dos fechados

        (setf estadosVisinhos (nextStates (node-state current))) ; nextestates de current-state
        (setf tamanho_estadosVizinhos (list-length (estadosVisinhos)))

        (dotimes (i tamanho_estadosVizinhos)                                              ;
            (setf visinho (make-node :parent current :state (nth i estadosVisinhos)))       ;PARA CRIAR LISTA COM TODOS NODES VIZINHOS DE CURRENT 
            (append (list(visinho)) listaVizinhos))                                         ;                    LISTAVIZINHOS

        (loop for vizinho in listaVizinhos do  
            (if (member vizinho closedSet) (continue))

            (setq tentative_gScore (+ (node-g current) (dist_between current vizinho)))   

            (if (not(member vizinho closedSet)) (append (list(vizinho)) openSet))          ;
            (if (>= (tentative_gScore) (node-g vizinho)) (continue))                       ; MAYBE CONDS AQUI

            (setq (node-g vizinho) tentative_gScore)
            (setq (node-f vizinho) (+ (node-g vizinho) (compute-heuristic (node-state vizinho))))
)
)

(return-from a* nil))

我的节点结构是：

;;; Definition of a search node
;;;  * parent - the parent node
;;;  * state - the state of the node
;;;  * f - estimate of the cost
;;;  * g - cost from the initial node to the current node
;;;  * h - estimate of the cost from the current node to the nearest goal
(defstruct node
   parent
   state
   f
   g
   h)

在我的翻译中，我使用其他功能，但我已经测试过并且是正确的。

当我尝试编译我的代码时，我收到语法错误，但我不知道在哪里..

编辑：错误讯息：

LOOP: illegal syntax near (setq tamanho_openS (list-length (openSet))) in loop (and then the terminal prints the entire loop)

Answer 1

您正在使用＆＃34;扩展＆＃34; loop表单，因此您需要执行

(loop while ...
  do ...)

而不是

(loop while ...
  ...)

错误告诉你：它需要while条件后的关键字，并找到了正文的第一个语句。

您可能需要更仔细地审核The LOOP Facility。

PS。在使用let进行设置之前，请使用with或loop，setq 绑定本地变量。否则你的变量是全局特价。

PPS。请正确缩进您的代码;你可以使用Emacs。

Clisp - 将伪代码转换为实际的lisp代码

1 个答案: