如何连接std :: string和int？ [英] How to concatenate a std::string and an int?

问题描述

我认为这很简单，但它会带来一些困难。如果我有

I thought this would be really simple but it's presenting some difficulties. If I have

std::string name = "John";
int age = 21;

如何组合它们以获得单个字符串John21？

How do I combine them to get a single string "John21"?

推荐答案

按字母顺序排列：

std::string name = "John";
int age = 21;
std::string result;

// 1. with Boost
result = name + boost::lexical_cast<std::string>(age);

// 2. with C++11
result = name + std::to_string(age);

// 3. with FastFormat.Format
fastformat::fmt(result, "{0}{1}", name, age);

// 4. with FastFormat.Write (requires #include <sstream>)
fastformat::write(result, name, age);

// 5. with the {fmt} library
result = fmt::format("{}{}", name, age);

// 6. with IOStreams
std::stringstream sstm;
sstm << name << age;
result = sstm.str();

// 7. with itoa
char numstr[21]; // enough to hold all numbers up to 64-bits
result = name + itoa(age, numstr, 10);

// 8. with sprintf
char numstr[21]; // enough to hold all numbers up to 64-bits
sprintf(numstr, "%d", age);
result = name + numstr;

// 9. with STLSoft's integer_to_string
char numstr[21]; // enough to hold all numbers up to 64-bits
result = name + stlsoft::integer_to_string(numstr, 21, age);

// 10. with STLSoft's winstl::int_to_string()
result = name + winstl::int_to_string(age);

// 11. With Poco NumberFormatter
result = name + Poco::NumberFormatter().format(age);

1. 是安全的，但很慢;需要 Boost （仅限标题）;大多数/所有平台


2. 是安全的，需要C ++ 11（ to_string（）已包含在 #include< string> ）


3. 是安全且快速的;需要 FastFormat ，必须编译;大多数/所有平台


4. 安全，快速;需要 FastFormat ，必须编译;大多数/所有平台


5. 安全，快速;需要 {fmt}库，可以在仅标题模式下编译或使用;大多数/所有平台


6. 安全，缓慢，详细;需要 #include< sstream> （来自标准C ++）


7. 很脆弱（你必须提供足够大的缓冲区），快，和冗长的; itoa（）是一个非标准扩展，并不保证可用于所有平台


8. 很脆弱（你必须提供足够大的缓冲区），快速，冗长;什么都不需要（标准C ++）;所有平台


9. 都很脆弱（你必须提供足够大的缓冲区），可能是最快的转换，详细;需要 STLSoft （仅限标题）;大多数/所有平台


10. safe-ish（你不要使用多个 int_to_string（）调用单个语句），快速;需要 STLSoft （仅限标题）;仅限Windows


11. 是安全的，但速度很慢;需要 Poco C ++ ;大多数/所有平台

1. is safe, but slow; requires Boost (header-only); most/all platforms
2. is safe, requires C++11 (to_string() is already included in #include <string>)
3. is safe, and fast; requires FastFormat, which must be compiled; most/all platforms
4. is safe, and fast; requires FastFormat, which must be compiled; most/all platforms
5. is safe, and fast; requires the {fmt} library, which can either be compiled or used in a header-only mode; most/all platforms
6. safe, slow, and verbose; requires #include <sstream> (from standard C++)
7. is brittle (you must supply a large enough buffer), fast, and verbose; itoa() is a non-standard extension, and not guaranteed to be available for all platforms
8. is brittle (you must supply a large enough buffer), fast, and verbose; requires nothing (is standard C++); all platforms
9. is brittle (you must supply a large enough buffer), probably the fastest-possible conversion, verbose; requires STLSoft (header-only); most/all platforms
10. safe-ish (you don't use more than one int_to_string() call in a single statement), fast; requires STLSoft (header-only); Windows-only
11. is safe, but slow; requires Poco C++ ; most/all platforms

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