用(格式)重复字符串/字符

Question

(format)在Common lisp中是否有重复指令,类似于(我知道这不起作用):

(format t "~5C" #\*)

只是想知道是否没有比这更优雅的方法:(来自rosettacode )

(defun repeat-string (n string)
  (with-output-to-string (stream)
    (loop repeat n do (write-string string stream))))

(princ (repeat-string 5 "hi"))

Answer 1

(defun write-repeated-string (n string stream)
  (loop repeat n do (write-string string stream)))

(write-repeated-string 5 "hi" *standard-output*))

通常,您可以使用格式迭代:

(format t "~v@{~A~:*~}" 5 "hi")

~A可以输出各种项目,而不仅仅是字符.有关更多信息,请参阅uselpa的链接答案.

上面从第一个参数获取迭代次数.因此v,波浪形的背后.

其余参数将由迭代消耗.因此@.

在迭代中,我们返回一个元素.因此~:*.

它类似于(format t "~v{~A~:*~}" 5 '("hi")),可能更容易理解.