Question

C++ 标准图书馆界定了这一功能,或者我是否不得不利用诱骗?

我搜索了这个网站,发现除波斯特以外的东西,但我认为我在这里提出更好的要求。

Answer 1

只是部分原因。

C++11 <string> has std::to_string for the built-in types:

[n3290:21.5/7]:
string to_string(int val);
string to_string(unsigned val);
string to_string(long val);
string to_string(unsigned long val);
string to_string(long long val);
string to_string(unsigned long long val);
string to_string(float val);
string to_string(double val);
string to_string(long double val);
Returns: Each function returns a string object holding the character representation of the value of its argument that would be generated by calling sprintf(buf, fmt, val) with a format specifier of "%d", "%u", "%ld", "%lu", "%lld", "%llu", "%f", "%f", or "%Lf", respectively, where buf designates an internal character buffer of sufficient size.

下面还有一段路要走:

[n3290:21.5/1, 21.5/4]:

int stoi(const string& str, size_t *idx = 0, int base = 10);
long stol(const string& str, size_t *idx = 0, int base = 10);
unsigned long stoul(const string& str, size_t *idx = 0, int base = 10);
long long stoll(const string& str, size_t *idx = 0, int base = 10);
unsigned long long stoull(const string& str, size_t *idx = 0, int base = 10);
float stof(const string& str, size_t *idx = 0);
double stod(const string& str, size_t *idx = 0);
long double stold(const string& str, size_t *idx = 0);

但是,你可以使用什么通用(至少,直到T2,可能!)和C++03中根本没有使用。

Answer 2

即便在C++11中,也没有任何斜线,但

Answer 3

这里没有 st脚:结构-播,但你总是能够做与。

template <typename T>
T lexical_cast(const std::string& str)
{
    T var;
    std::istringstream iss;
    iss.str(str);
    iss >> var;
    // deal with any error bits that may have been set on the stream
    return var;
}

Answer 4

No it s a pure Boost thing only.

Answer 5

如果您不希望提升,那么一个称为 fmt 。执行如下:

// Works with all the C++11 features and AFAIK faster then boost or standard c++11
std::string string_num = fmt::format_int(123456789).str(); // or .c_str()

http://fmtlib.net/latest/syntax.html#format-examples” rel=“nofollow noreferer” 官方网页。

以立场取证:

format("{0}, {1}, {2}",  a ,  b ,  c );
// Result: "a, b, c"
format("{}, {}, {}",  a ,  b ,  c );
// Result: "a, b, c"
format("{2}, {1}, {0}",  a ,  b ,  c );
// Result: "c, b, a"
format("{0}{1}{0}", "abra", "cad");  // arguments  indices can be repeated
// Result: "abracadabra"

2. 修改案文并具体说明一个宽松之处:

format("{:<30}", "left aligned");
// Result: "left aligned                  "
format("{:>30}", "right aligned");
// Result: "                 right aligned"
format("{:^30}", "centered");
// Result: "           centered           "
format("{:*^30}", "centered");  // use  *  as a fill char
// Result: "***********centered***********"

替换 %+f, %-f, % f, 并注明:

format("{:+f}; {:+f}", 3.14, -3.14);  // show it always
// Result: "+3.140000; -3.140000"
format("{: f}; {: f}", 3.14, -3.14);  // show a space for positive numbers
// Result: " 3.140000; -3.140000"
format("{:-f}; {:-f}", 3.14, -3.14);  // show only the minus -- same as  {:f}; {:f} 
// Result: "3.140000; -3.140000"

将百分率和百分率重新计算,并将价值转换成不同的依据:

format("int: {0:d};  hex: {0:x};  oct: {0:o}; bin: {0:b}", 42);
// Result: "int: 42;  hex: 2a;  oct: 52; bin: 101010"
// with 0x or 0 or 0b as prefix:
format("int: {0:d};  hex: {0:#x};  oct: {0:#o};  bin: {0:#b}", 42);
// Result: "int: 42;  hex: 0x2a;  oct: 052;  bin: 0b101010"

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