在Lisp中，+函数实际上可以有多少输入? [英] In Lisp, how many inputs can the + function actually have?

问题描述

我对Lisp比较陌生，我想知道"+"功能是否真的有上限.

I'm relatively new to Lisp, and I was wondering if there really is an upper limit to the "+" function.

(我想这适用于所有其他算术函数-"，"/"等)

(I guess this applies to all the other arithmetic functions "-", "/" etc.)

推荐答案

是的，有一个上限，但是确切的上限取决于实现.您可以保证至少通过50次，但这要视情况而定.如果您需要汇总列表，最好使用(reduce #'+ list)，这应该比其他任何方法都具有更好的可伸缩性.

Yes, there is an upper limit, but the exact upper limit is implementation-dependent. You're guaranteed to be able to pass at least 50, but it all depends. If you need to sum a list, you're probably better off with (reduce #'+ list), that should give you a much better scalability than any other method.

通用Lisp HyperSpec 有更多信息.

当涉及到值范围时，有两种不同的情况，即浮点数和整数.浮点数本身受大小限制，从单浮点数更改为双浮点数的实现会使我感到非常惊讶.使用整数和有理数，CL在fixnum和bignum之间无缝转换，因此限制是实现可使用的可用地址空间的函数.我怀疑复数是否成立(复数和有理数->如果需要，请转至bignums；复数浮点数->表示超出范围，或者返回Inf或NaN).

When it comes to value ranges there are two distinct cases, floats and integers. Floats are inherently limited by their size and an implementation that changed from single-floats to double-floats would surprise me a lot. With integers and rationals, CL seamlessly transition between fixnums and bignums, so the limit is a function of the usable address space available to the implementation. I suspect the same holds for complex numbers (complex integers and rationals -> go to bignums if needed; complex floats -> signal an out of range, or return an Inf or NaN).

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