std::basic_string<CharT,Traits,Allocator>:: find_first_of

Finds the first character equal to one of the characters in the given character sequence. The search considers only the range [ pos , size() ) . If none of the characters in the given character sequence is present in the range, npos will be returned.

Parameters

Return value

Position of the found character or npos if no such character is found.

Exceptions

If an exception is thrown for any reason, this function has no effect ( strong exception safety guarantee ).

Notes

Traits :: eq ( ) is used to perform the comparison.

Example

#include <cassert>
#include <iostream>
#include <string>
#include <string_view>
 
int main()
{
    using namespace std::literals;
    std::string::size_type sz;
 
    // (1)
    sz = "alignas"s.find_first_of("klmn"s);
    //     └────────────────────────┘
    assert(sz == 1);
 
    sz = "alignof"s.find_first_of("wxyz"s);
    // no match
    assert(sz == std::string::npos);
 
    // (2)
    sz = "consteval"s.find_first_of("xyzabc", 0, 3);
    // no match (× are not targets)     ×××
    assert(sz == std::string::npos);
 
    sz = "consteval"s.find_first_of("xyzabc", 0, 6);
    //    └───────────────────────────────┘
    assert(sz == 0);
 
    // (3)
    sz = "decltype"s.find_first_of("xyzabc");
    //      └────────────────────────────┘
    assert(sz == 2);
 
    // (4)
    sz = "co_await"s.find_first_of('a');
    //       └──────────────────────┘
    assert(sz == 3);
 
    // (5)
    sz = "constinit"s.find_first_of("int"sv);
    //      └─────────────────────────┘
    assert(sz == 2);
 
    std::cout << "All tests passed.\n";
}

All tests passed.

Defect reports

The following behavior-changing defect reports were applied retroactively to previously published C++ standards.

See also