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std::numeric_limits<T>::max

Defined in header <limits>
static T max() throw();
(until C++11)
static constexpr T max() noexcept;
(since C++11)

Returns the maximum finite value representable by the numeric type T. Meaningful for all bounded types.

Return value

T std::numeric_limits<T>::max()
/* non-specialized */ T()
bool true
char CHAR_MAX
signed char SCHAR_MAX
unsigned char UCHAR_MAX
wchar_t WCHAR_MAX
char8_t (since C++20) UCHAR_MAX
char16_t (since C++11) UINT_LEAST16_MAX
char32_t (since C++11) UINT_LEAST32_MAX
short SHRT_MAX
unsigned short USHRT_MAX
int INT_MAX
unsigned int UINT_MAX
long LONG_MAX
unsigned long ULONG_MAX
long long (since C++11) LLONG_MAX
unsigned long long (since C++11) ULLONG_MAX
float FLT_MAX
double DBL_MAX
long double LDBL_MAX

Example

Demonstrates the use of max() with some fundamental types and some standard library typedefs (the output is system-specific):

#include <cstddef>
#include <iostream>
#include <limits>
#include <string_view>
#include <type_traits>
 
template<typename T>
void print_max_twice(std::string_view type)
{
    constexpr T max_value {std::numeric_limits<T>::max()};
 
    std::cout << type << ": ";
    if constexpr (std::is_floating_point_v<T>)
        std::cout << std::defaultfloat << max_value << " or "
                  << std::hexfloat << max_value << '\n';
    else
        std::cout << std::dec << static_cast<unsigned long long>(max_value) << " or "
                  << std::hex << static_cast<unsigned long long>(max_value) << '\n';
}
 
int main()
{
    std::cout << std::showbase;
 
    print_max_twice<bool>("bool");
    print_max_twice<short>("short");
    print_max_twice<int>("int");
    print_max_twice<std::streamsize>("streamsize");
    print_max_twice<std::size_t>("size_t");
    print_max_twice<char>("char");
    print_max_twice<char16_t>("char16_t");
    print_max_twice<wchar_t>("wchar_t");
    print_max_twice<float>("float");
    print_max_twice<double>("double");
    print_max_twice<long double>("long double");
}

Possible output:

bool: 1 or 0x1
short: 32767 or 0x7fff
int: 2147483647 or 0x7fffffff
streamsize: 9223372036854775807 or 0x7fffffffffffffff
size_t: 18446744073709551615 or 0xffffffffffffffff
char: 127 or 0x7f
char16_t: 65535 or 0xffff
wchar_t: 2147483647 or 0x7fffffff
float: 3.40282e+38 or 0x1.fffffep+127
double: 1.79769e+308 or 0x1.fffffffffffffp+1023
long double: 1.18973e+4932 or 0xf.fffffffffffffffp+16380

See also

[static] (C++11)
returns the lowest finite value of the given type
(public static member function)
[static]
returns the smallest finite value of the given type
(public static member function)

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https://en.cppreference.com/w/cpp/types/numeric_limits/max