什么是浮点错误-1＃Ĵ是什么意思？ [英] What does floating point error -1.#J mean?

问题描述

近日，有时（很少），当我们从我们的应用程序中导出数据，导出日志包含看起来像浮点值-1。＃J。我一直无法重现它，所以我不知道浮动样子二进制，或者如何Visual Studio中显示出来。

Recently, sometimes (rarely) when we export data from our application, the export log contains float values that look like "-1.#J". I haven't been able to reproduce it so I don't know what the float looks like in binary, or how Visual Studio displays it.

我试图查看源$ C ​​$ c代表的printf，但没有发现任何东西（不是100％肯定我看着正确的版本，虽然...）。

I tried looking at the source code for printf, but didn't find anything (not 100% sure I looked at the right version though...).

我试过，但谷歌搜索谷歌丢弃任何＃，它似乎。而且我找不到浮动错误的任何名单。

I've tried googling but google throws away any #, it seems. And I can't find any lists of float errors.

推荐答案

它可以是负无穷大或NaN（非数字）。由于在球场上的printf的格式不区分它们。

It can be either negative infinity or NaN (not a number). Due to the formatting on the field printf does not differentiate between them.

我尝试以下code在Visual Studio 2008：

I tried the following code in Visual Studio 2008:

double a = 0.0;
printf("%.3g\n", 1.0 / a);  // +inf
printf("%.3g\n", -1.0 / a); // -inf
printf("%.3g\n", a / a);    //  NaN

这会导致下面的输出：

which results in the following output:

1.#J
-1.#J
-1.#J

删除.3格式说明符给出了：

removing the .3 formatting specifier gives:

1.#INF
-1.#INF
-1.#IND

所以很清楚0/0给人楠-1/0给出了负无穷大（南安，-INF和+ INF是唯一的错误浮点数，如果我没有记错）

so it's clear 0/0 gives NaN and -1/0 gives negative infinity (NaN, -inf and +inf are the only "erroneous" floating point numbers, if I recall correctly)

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