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{{cpp/title|popcount}}
{{cpp/utility/bit/navbar}}
{{ddcl|header=bit|since=c++20|
template< class T >
constexpr int popcount( T x ) noexcept;
}}

Returns the number of {{c|1}} bits in the value of {{c|x}}.

{{cpp/enable_if|{{tt|T}} is an unsigned integer type (that is, {{c/core|unsigned char}}, {{c/core|unsigned short}}, {{c/core|unsigned int}}, {{c/core|unsigned long}}, {{c/core|unsigned long long}}, or an extended unsigned integer type)}}.

===Parameters===
{{par begin}}
{{par|x|value of unsigned integer type}}
{{par end}}

===Return value===
The number of {{c|1}} bits in the value of {{c|x}}.

===Notes===
{{petty|The name {{tt|popcount}} is a contraction for “population count”.}}

{{feature test macro|__cpp_lib_bitops|std=C++20|value=201907L|[[cpp/utility/bit|Bit operations]]}}

===Example===
{{example
|code=
#include <bit>
#include <bitset>
#include <cstdint>
#include <iostream>

static_assert(std::popcount(0xFULL) == 4);

int main()
{
    for (const std::uint8_t x : {0, 0b00011101, 0b11111111})
        std::cout << "popcount( " << std::bitset<8>(x) << " ) = "
                  << std::popcount(x) << '\n';
}
|output=
popcount( 00000000 ) = 0
popcount( 00011101 ) = 4
popcount( 11111111 ) = 8
}}

===See also===
{{dsc begin}}
{{dsc inc|cpp/numeric/dsc countl_zero}}
{{dsc inc|cpp/numeric/dsc countl_one}}
{{dsc inc|cpp/numeric/dsc countr_zero}}
{{dsc inc|cpp/numeric/dsc countr_one}}
{{dsc inc|cpp/numeric/dsc has_single_bit}}
{{dsc inc|cpp/utility/bitset/dsc count}}
{{dsc inc|cpp/utility/bitset/dsc all_any_none}}
{{dsc end}}

{{langlinks|es|ja|ru|zh}}

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