Read the question carefully. Phil wants a MINIMUM of 1 digit of precision after the decimal point, but more if there is non-zero digits.

仔细阅读问题。Phil希望小数点后的精度至少为1位，但如果有非零位数，则精度更高。

@Phil: You might find stackoverflow.com/questions/2475642/… helpful.

@菲尔：你可能会找到Stackoverflow.com/Questions/2475642/…很有帮助。

Thanks Roger. That's very helpful. Your formatter example looks like the right way to go.

谢谢，罗杰。这很有帮助。您的格式化程序示例看起来是正确的方法。

Thanks Sameer. However that assumes that I know beforehand that d=0. Is there a solution for an arbitrary d that would print "0.0" if d=0, but "0.123456789" if d=0.123456789?

谢谢你，萨米尔。但这是假设我事先知道d=0。对于任意的d，如果d=0，则打印“0.123456789”，如果d=0.123456789，则打印“0.123456789”，是否有解决方案？

@Phil: The stream only has one precision setting. You could check the value before you output it, and output your "0.0" then (note that is a string literal, not a double).

@Phil：流只有一个精度设置。您可以在输出之前检查该值，然后输出您的“0.0”(请注意，这是一个字符串文字，而不是双精度)。

You can do something like this. cout << setprecision(d?9:1) << fixed << d << endl;

你可以做这样的事情。Cout<<设置精度(d？9：1)<<固定<

Nice shortcut. Might be a bit cumbersome in implementation as I'd need to have a setprecision call in every output stream.

很好的捷径。在实现中可能有点麻烦，因为我需要在每个输出流中都有一个设置精度调用。

@Phil: if (d) cout << d; else cout << "0.0"; is better (and you'd keep the stream with the desired fixed/precision settings, you don't have to repeat those unless they changed since the last output). Also realize you might want something like if (fabs(d) > some_tolerance) because floating point math is inexact.

@Phil：如果(D)cout<Some_Terance)的内容，因为浮点数学是不精确的。

+1, though it's still unclear to me what he wants exactly, beyond zero being exactly "0.0".

+1，尽管我仍然不清楚他到底想要什么，超过零正好是“0.0”。

Nothing more than that, Roger. I have a requirement that floats or double are represented in the output stream with a decimal place and I'm just looking for a way to do this elegantly without implying the kind of accuracy precision that Oddthinking refers to above. Hence 0 should be represented as 0.0, not 0.0000...

仅此而已，罗杰。我有一个要求，浮点数或双精度数在输出流中用小数位表示，我只是在寻找一种方法来优雅地实现这一点，而不暗示OddThink上面提到的那种精确度。因此，0应表示为0.0，而不是0.0000...

@Phil: What about 0.12, is output as "0.120000" okay? Why isn't "0.000000" fine? (Exactly what requirement does it fail?)

@Phil：如果是0.12，输出为“0.120000”可以吗？为什么“0.000000”不行？(它到底不能满足什么要求？)

If I had the option of setting a minimum precision then I could just set a maximum precision (setprecision(9)) and have the best of both worlds. 0.12 output as "0.12" while 0.123456789 is output as "0.123456789". As to why 0.000000 isn't fine? Unfortunately that's a convoluted story involving legacy implementations and historic data.

如果我可以选择设置一个最小精度，那么我只需要设置一个最大精度(设置精度(9))，就可以两全其美了。0.12输出为“0.12”，而0.123456789输出为“0.123456789”。为什么0.000000不好呢？不幸的是，这是一个涉及遗留实现和历史数据的复杂故事。

@Phil: If you merely need 0.0 treated specially, then do only that, but make sure you know why using fabs (as I showed in another comment) is useful. If you need to strip all trailing zeros, the question I linked (in the comment on the question above) will work. (And maybe you could edit the question with the clearer requirements and someone can add/edit an answer to match them.)

@Phil：如果你只需要特别处理0.0，那么就只做这件事，但要确保你知道为什么使用FABS(正如我在另一条评论中所展示的)是有用的。如果您需要去掉所有尾随的零，我链接的问题(在上面问题的评论中)将起作用。(也许您可以编辑具有更明确要求的问题，然后有人可以添加/编辑答案以匹配这些要求。)