Perl 中是否有 inf 常量? [英] Is there an inf constant in Perl?

问题描述

我正在为算法初始化一个具有无穷大的列表.编写 $x = 9**9**9 感觉很不直观，而且，我将来可能想使用 BigInt.1/0 抛出错误.

I'm initialising a list with infinities for an algorithm. Writing $x = 9**9**9 feels unintuitive, and also, I might want to use BigInt in the future. 1/0 throws an error.

获得 inf 的规范方法是什么?

What's the canonical way to get inf?

推荐答案

您可以使用特殊字符串 "inf":

You can use the special string "inf":

perl -E'say "inf" + 1'
inf
perl -E'say 1 / "inf"'
0

等等.

其他特殊字符串包括+inf、-inf、nan.当然，这也适用于 bignum 或 bigint 编译指示.但是，这些编译指示导出等效函数 inf 和 NaN，以便您可以使用裸字.

Other special strings include +inf, -inf, nan. Of course this also works with bignum or bigint pragmas. However, these pragmas export equivalent functions inf and NaN so that you can use barewords.

正如@ikegami 指出的那样，似乎没有一种便携 的方法可以在没有模块的情况下实现真正的无穷大.我刚刚浏览了这个有趣的 perlmonks 线程，但它并没有减少混乱.也许最好的解决方案是接受性能损失并从一开始 使用 big{num,int,rat}，但使用 no big{num,int,rat}在不需要它们的范围内.

As @ikegami pointed out, there doesn't seem to be a portable way of accomplishing true infinities without a module. I just waded through this interesting perlmonks thread, but it doesn't get less confusing. Perhaps the best solution would be to accept the performance penalty and use big{num,int,rat} from the start, but use no big{num,int,rat} in scopes where they aren't required.

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