std::experi...nd_last_set(3)

💅 NAME 💅

okay so this is the std::experi...nd_last_set(3) page from the C++ Standard Libary section, and the name line is literally:

std::experimental::find_first_set,std::experimental::find_last_set - std::experimental::find_first_set,std::experimental::find_last_set

yes bestie, it's one page for two functions: std::experimental::find_first_set and std::experimental::find_last_set. iconic. 👑

✨ Synopsis ✨

Defined in header <experimental/simd>

template< class T, class Abi >                    (1) (parallelism TS v2)
int find_first_set( const simd_mask<T, Abi>& k );
template< class T, class Abi >                    (2) (parallelism TS v2)
int find_last_set( const simd_mask<T, Abi>& k );

So:

1. find_first_set returns the lowest index i where k[i] is true. 🫶
2. find_last_set returns the greatest index i where k[i] is true. 💖

⚠️ warning bestie: the behavior is undefined if any_of(k) is false. fr fr, do not play with that. 💀

🎀 Parameters 🎀

• k — the simd_mask to apply the reduction to. that's the whole parameter list, no cap. 🎀

👑 Return value 👑

an int in the range [0, simd_size_v<T, Abi>). slay. ✨

🦋 Example 🦋

// Run this code

#include <cstddef>
#include <experimental/simd>
#include <iostream>

namespace stdx = std::experimental;

template<typename Abi>
int find(stdx::simd_mask<Abi> const& v)
{
    if (stdx::any_of(v))
        return find_first_set(v);
    return -1;
}

int main()
{
    stdx::simd_mask<short> a{0};
    a[2] = a[a.size() - 2] = 1;

    for (std::size_t i = 0; i < a.size(); ++i)
        std::cout << a[i] << ' ';
    std::cout << '\n';

    std::cout << "find_first_set: " << stdx::find_first_set(a) << '\n';
    std::cout << "find_last_set: " << stdx::find_last_set(a) << '\n';
    std::cout << "find: " << find(a) << '\n';
    a[2] = 0;
    std::cout << "find: " << find(a) << '\n';
    a[a.size() - 2] = 0;
    std::cout << "find: " << find(a) << '\n';
}

🌈 Possible output 🌈

0 0 1 0 0 0 1 0
find_first_set: 2
find_last_set: 6
find: 2
find: 6
find: -1

okay bye bestie 🫶 this page is from http://cppreference.com, version/date 2024.06.10, and the manual name is std::experi...nd_last_set(3). now go find those set bits, periodt. 💖✨