编写一个函数来取一个整数并返回一个包含格式化版本的std :: sting [英] Write a function to take an integer and return a std::sting containing a formatted version

问题描述

你好窥视。



我只想拿一个整数并返回一个字符串，其格式包括逗号。



我不关心语言环境，我只想要它包含逗号。



我正在使用C ++ 11并且代码将运行在其他。我需要用Google搜索并试用我找到的无数解决方案，但有些不起作用（特别是那些带有语言环境），有些甚至没有编译，其他只是使用标准输出而不是字符串。



它应该是简单的，当然？



（我是新的为了C ++ BTW所以要温柔！）



并且请尝试解雇你有什么尝试告诉我们你的代码等评论 - 这里有点意思我向你展示一页又一页不起作用的代码。



我会对一些只是循环字符串的东西感到满意，将一个额外的逗号连接到坦率地说，每三个字符输出一个字符串 - 即便如此当我尝试它时引起异常 - 但这可能是因为我不知道如何正确地迭代std :: string！

Hello peeps.

I just want to take an integer and return a string with the formatting to include commas.

I don't care about locale, I just want it to include commas.

I am using C++ 11 and the code will run on an iDevice.

I have googled and tried umpteen solutions I found, but some don't work (specifically those with locales) and some don't even compile, others just use std output rather than strings.

It should be simples, surely?

(I am new to C++ BTW so be gentle !)

And please try to lay off the "what have you tried" "show us your code" etc. comments - there's little point me showing you page after page of code that doesn't work.

I'd be happy with something that just loops through a string, concatenating an extra comma into and output string every three characters, frankly - even that seemed to cause an exception when I tried it - but that's probably because I don't know how to iterate over a std::string properly!

推荐答案

从迭代开始字符串：这很简单！ std :: string有一个operator []重载，所以你可以逐个访问每个字符：

Start by iterating over the string: that's easy! std::string has an operator[] overload, so you can access each character one-by-one:

std::string myStr = "Hello!";
for(unsigned int i = 0; i < myStr.length(); i++)
    {
    char c = myStr[i]; //this is your character
    cout << c;
    }

所以...在每三个字符后添加一个逗号？实际上并不复杂：

So...adding a comma after each three characters? Not complex, really:

int commaAt = 3;
std::string myStr = "Hello there!";
for(unsigned int i = 0; i < myStr.length(); i++)
    {
    if (commaAt == 0)
        {
        cout << ',';
        commaAt = 3;
        }
    char c = myStr[i]; //this is your character
    cout << c;
    commaAt--;
    }

如果我想要返回一个字符串而不是cout-ing怎么能我这样做了吗？

你做的几乎就是你所展示的，但是试图将这些字符连接到另一个我开始异常的字符串......



当你想到你在做什么时，这也很容易：

"if i wanted to return a string rather than cout-ing how can i do that?
It was doing pretty much what you show, but trying to concat the chars to another string where I started to get exceptions..."

That's also pretty easy, when you think about what you are doing:

int commaAt = 3;
std::string myStr = "Hello there!";
std::string output = "";
for(unsigned int i = 0; i < myStr.length(); i++)
    {
    if (commaAt == 0)
        {
        output += ',';
        commaAt = 3;
        }
    commaAt--;
    char c = myStr[i]; //this is your character
    output += c;
    }

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