要使fold-left和fold-right达到同样的结果，要求op对操作顺序无关，譬如+
(define (accumulate op initial sequence)
(if (null? sequence)
initial
(op (car sequence)
(accumulate op initial (cdr sequence)))))
(define fold-right accumulate)
(define (fold-left op initial sequence)
(define (iter result rest)
(if (null? rest)
result
(iter (op result (car rest))
(cdr rest))))
(iter initial sequence))
(newline)
(display (fold-right / 1 (list 1 2 3)))
(newline)
(display (fold-left / 1 (list 1 2 3)))
(newline)
(display (fold-right list '() (list 1 2 3)))
(newline)
(display (fold-left list '() (list 1 2 3)))
(newline)
(display (fold-right + 0 (list 1 2 3)))
(newline)
(display (fold-left + 0 (list 1 2 3)))
本文探讨了fold-left和fold-right函数的实现及其在不同运算符下的行为一致性。通过具体的代码示例，展示了如何定义这些函数，并比较了它们在使用加法等结合运算符时的相同结果。
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