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std::basic_string_view::find_first_of(3) | C++ Standard Libary | std::basic_string_view::find_first_of(3) |
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>)
2022.07.31 | http://cppreference.com |