# std::numeric_limits<T>::infinity

< cpp‎ | types‎ | numeric limits

static T infinity() throw(); |  | (C++11 前)
static constexpr T infinity() noexcept; |  | (C++11 起)

返回浮点类型 `T` 所表示的特殊值“正无穷大”。仅若 std::numeric_limits<T>::has_infinity == true 才有意义。在最常见的浮点数二进制表示 IEEE 754 中，正无穷大是所有指数位为 1 而所有尾数位为 0 的值。

### 返回值

`T` | std::numeric_limits<T>::infinity()
/* non-specialized */ | `T()`
bool | false
char | ​0​
signed char | ​0​
unsigned char | ​0​
wchar_t | ​0​
char8_t (C++20) | ​0​
char16_t (C++11) | ​0​
char32_t (C++11) | ​0​
short | ​0​
unsigned short | ​0​
int | ​0​
unsigned int | ​0​
long | ​0​
unsigned long | ​0​
long long (C++11) | ​0​
unsigned long long (C++11) | ​0​
float | HUGE_VALF
double | HUGE_VAL
long double | HUGE_VALL

### 示例

    #include <iostream>
    #include <limits>
    int main()
    {
        double max = std::numeric_limits<double>::max();
        double inf = std::numeric_limits<double>::infinity();

        if(inf > max)
            std::cout << inf << " is greater than " << max << '\n';
    }

输出：

    inf is greater than 1.79769e+308

### 参阅

has_infinity [静态] | 鉴别能表示特殊值“正无穷大”的浮点类型 (公开静态成员常量)