如何将逗号设置为小数点? [英] How can I set the comma to be a decimal point?
问题描述
我想读和写pi为3,141592而不是3.141592,因为它在许多欧洲国家是常见的。我如何用iostreams完成这个?换句话说,
I would like to read and write pi as 3,141592 instead of 3.141592 as it is common in many european countries. How can I accomplish this with iostreams? In other words
cout << 3.141592;
应打印
3,141592
推荐答案
您应该使用 basic_ios :: imbue
设置首选区域。
You should use basic_ios::imbue
to set the preferred locale.
查看这里: http:// www.cplusplus.com/reference/ios/ios_base/imbue/
区域设置允许您使用用户首选的方式,因此,如果计算机意大利使用逗号分隔十进制数字,在美国,点仍然使用。使用语言环境是一个好习惯。
Locales allow you to use the preferred way by the user, so if a computer in Italy uses comma to separate decimal digits, in the US the dot is still used. Using locales is a Good Practice.
但是如果你想明确强制使用逗号,看看这里:
http://www.cplusplus.com/reference/locale/numpunct/decimal_point/
But if you want to explicitly force the use of the comma, take a look here: http://www.cplusplus.com/reference/locale/numpunct/decimal_point/
这里有一个小例子,我刚刚使用g ++强制执行char','(传递分隔符作为模板参数只是为了有趣,而不是真的必要)
Here a small example I just made with g++ which enforces the char ',' (passing the separator as template argument is just for fun, not really necessary)
#include <iostream>
#include <locale>
template <class charT, charT sep>
class punct_facet: public std::numpunct<charT> {
protected:
charT do_decimal_point() const { return sep; }
};
int main(int argc, char **argv) {
std::cout.imbue(std::locale(std::cout.getloc(), new punct_facet<char, ','>));
std::cout << "My age is " << 3.1415 << " lightyears.\n";
}
请注意,使用 cout.getloc code>我正在覆盖当前设置的区域设置中的一个方面,也就是说,在cout的当前区域设置中,我只改变标点符号的处理方式。
Note that using cout.getloc()
I'm overriding just a single facet in the currently set locale, that is, in the current locale settings of cout, I'm changing only how the punctuation is done.
do_decimal_point
是 std :: numpunct
的虚函数,您可以重新定义以提供自定义分隔器。在打印您的号码时, numpunct :: decimal_point
将使用此虚拟函数。
do_decimal_point
is a virtual function of std::numpunct
that you can redefine to provide your custom separator. This virtual function will be used by numpunct::decimal_point
when printing your number.
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