如何将C ++字符串转换为大写 [英] How to Convert a C++ String to Uppercase

问题描述

我需要将C ++中的字符串转换为完全大写.我搜索了一段时间，发现了一种解决方法:

I need to convert a string in C++ to full upper case. I've been searching for a while and found one way to do it:

#include <iostream>
#include <algorithm> 
#include <string>  

using namespace std;

int main()
{
    string input;
    cin >> input;

    transform(input.begin(), input.end(), input.begin(), toupper);

    cout << input;
    return 0;
}

不幸的是，这不起作用，我收到了以下错误消息:

Unfortunately this did not work and I received this error message:

没有匹配函数可调用'transform(std :: basic_string :: iterator，std :: basic_string :: iterator，std :: basic_string :: iterator，

no matching function for call to 'transform(std::basic_string::iterator, std::basic_string::iterator, std::basic_string::iterator,

我尝试了其他同样行不通的方法.这是最接近工作的地方.

I've tried other methods that also did not work. This was the closest to working.

所以我要问的是我做错了什么.也许我的语法不好，或者我需要添加一些内容.我不确定.

So what I'm asking is what I am doing wrong. Maybe my syntax is bad or I need to include something. I am not sure.

我在这里获得了大部分信息: http://www.cplusplus.com/forum/beginner/75634/(最后两个帖子)

I got most of my info here: http://www.cplusplus.com/forum/beginner/75634/ (last two posts)

推荐答案

您需要在 toupper 之前加一个双冒号:

You need to put a double colon before toupper:

transform(input.begin(), input.end(), input.begin(), ::toupper);

---

说明:

有两种不同的 toupper 函数:

toupper (通过 :: toupper 访问). std 名称空间中的

toupper (通过 std :: toupper 访问)具有多个重载，因此不能简单地引用仅带有名称.您必须将其显式转换为特定的函数签名才能被引用，但是获取函数指针的代码看起来很丑: static_cast< int(*)(int)>(& std :: toupper)

toupper in the std namespace (accessed with std::toupper) which has multiple overloads and thus cannot be simply referenced with a name only. You have to explicitly cast it to a specific function signature in order to be referenced, but the code for getting a function pointer looks ugly: static_cast<int (*)(int)>(&std::toupper)

由于您正在使用命名空间std ，因此在编写 toupper 时，2.隐藏1.并根据名称解析规则进行选择.

Since you're using namespace std, when writing toupper, 2. hides 1. and is thus chosen, according to name resolution rules.

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