[英]Tail-Call sum-of-squares-recursive function Racket
I am trying to write a tail-call recursive function to find the sum of squares that are in a list.我正在尝试编写尾调用递归 function 来查找列表中的平方和。 I have some code that works but currently, it is a non-tail-call function. How would I change it to be tailed?
我有一些有效的代码,但目前它是一个非尾调用 function。我如何将其更改为尾调用?
(define sum-of-squares
(lambda (lst)
(if (null? lst)
0
(+ (* (car lst) (car lst)) (sumsquares (cdr lst)))
)))
The usual way to convert a function that accumulates results to tail recursion is by moving the accumulator into a parameter.将累加结果的 function 转换为尾递归的常用方法是将累加器移动到参数中。 In the code below, the
sum
parameter accumulates the sums of squares.在下面的代码中,
sum
参数累加平方和。
(define sum-of-squares
(lambda (lst)
(define recursive-sos
(lambda (lst sum)
(if (null? lst)
sum
(recursive-sos (cdr lst)
(+ (* (car lst) (car lst))
sum)))))
(recursive-sos lst 0)))
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