替换lisp中的函数

Question

我想在给定的列表中替换单词，但是当替换单词是由列表给出的时候，这是非常困难的

例如(myreplace‘((狗猫)(可爱可爱))’(我的狗很可爱)) -> (我的猫很可爱)

帮帮我!

Answer 1

下面是一个递归版本：

(defun myreplace (subst-alist replace-in)
  (when replace-in
    (let ((found (assoc (car replace-in) subst-alist :test #'eq)))
      (cons 
       (if found
           (cadr found)
         (car replace-in))
       (myreplace subst-alist (cdr replace-in))))))

如果你更喜欢这种方法，这里有一个迭代版本：

(defun myreplace (subst-alist replace-in)
  (let (result)
    (dolist (word replace-in (reverse result))
      (let ((found (assoc word subst-alist :test #'eq)))
        (push (if found (cadr found) word)
              result)))))

Answer 2

下面是一个解决方案，它使用reduce为每个新旧对调用substitute，以增量方式转换原始序列：

(defun myreplace (substitutions sequence)
  (reduce (lambda (seq substitution)
            (destructuring-bind (old new) substitution
              (substitute new old seq)))
          substitutions
          :initial-value sequence))

编辑:Trey使用assoc (不是assq，这是Emacs Lisp)来查找替换的想法非常好。通过使用内置支持构建新列表的运算符，即带有collect子句的mapcar或loop，可以简化该操作：

(defun myreplace (substitutions list)
  (mapcar (lambda (elt)
            (let ((substitution (assoc elt substitutions)))
              (if substitution
                  (second substitution)
                  elt)))
          list))

或

(defun myreplace (substitutions list)
  (loop for elt in list
     for substitution = (assoc elt substitutions)
     when substitution collect (second substitution)
     else collect elt))