NAME¶

std::basic_string_view::find_first_of - std::basic_string_view::find_first_of

Synopsis¶

constexpr size_type find_first_of( basic_string_view v, size_type (1) (since C++17)
pos = 0 ) const noexcept;
constexpr size_type find_first_of( CharT c, size_type pos = 0 ) (2) (since C++17)
const noexcept;
constexpr size_type find_first_of( const CharT* s, size_type pos, (3) (since C++17)
size_type count ) const;
constexpr size_type find_first_of( const CharT* s, size_type pos = (4) (since C++17)
0 ) const;

Finds the first character equal to any of the characters in the given character
sequence.

1) Finds the first occurrence of any of the characters of v in this view, starting
at position pos.
2) Equivalent to find_first_of(basic_string_view(std::addressof(c), 1), pos).
3) Equivalent to find_first_of(basic_string_view(s, count), pos).
4) Equivalent to find_first_of(basic_string_view(s), pos).

Parameters¶

v - view to search for
pos - position at which to start the search
count - length of the string of characters to search for
s - pointer to a string of characters to search for
c - character to search for

Return value¶

Position of the first occurrence of any character of the substring, or npos if no
such character is found.

Complexity¶

O(size() * v.size()) at worst.

Example¶

// Run this code

#include <string_view>
#include <iostream>

int main()
{
using namespace std::literals;
constexpr auto N = std::string_view::npos;

auto is_white_space = [](const char c) noexcept {
return " \t\n\f\r\v"sv.find_first_of(c) != N;
};

static_assert(
1 == "alignas"sv.find_first_of("klmn"sv) &&
// └─────────────────────────┘
N == "alignof"sv.find_first_of("wxyz"sv) &&
//
3 == "concept"sv.find_first_of("bcde"sv, /* pos= */ 1) &&
// └───────────────────────┘
N == "consteval"sv.find_first_of("oxyz"sv, /* pos= */ 2) &&
//
6 == "constexpr"sv.find_first_of('x') &&
// └─────────────────────┘
N == "constinit"sv.find_first_of('x') &&
//
6 == "const_cast"sv.find_first_of('c', /* pos= */ 4) &&
// └──────────────────────┘
N == "continue"sv.find_first_of('c', /* pos= */ 42) &&
//
5 == "co_await"sv.find_first_of("cba", /* pos= */ 4) &&
// └───────────────────────┘
7 == "decltype"sv.find_first_of("def", /* pos= */ 2, /* count= */ 2) &&
// └────────────────────┘
N == "decltype"sv.find_first_of("def", /* pos= */ 2, /* count= */ 1) &&
//
is_white_space(' ') && is_white_space('\r') && !is_white_space('\a')
);
std::cout << "All tests passed.\n";
}

Output:¶

All tests passed.

See also¶

find find characters in the view
(C++17) (public member function)
rfind find the last occurrence of a substring
(C++17) (public member function)
find_last_of find last occurrence of characters
(C++17) (public member function)
find_first_not_of find first absence of characters
(C++17) (public member function)
find_last_not_of find last absence of characters
(C++17) (public member function)
find first occurrence of characters
find_first_of (public member function of
std::basic_string<CharT,Traits,Allocator>)