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std::basic_string_view<CharT,Traits>::npos

From cppreference.com
 
 
 
std::basic_string_view
 
static constexpr size_type npos = size_type(-1);
(since C++17)

This is a special value equal to the maximum value representable by the type size_type. The exact meaning depends on context, but it is generally used either as end of view indicator by the functions that expect a view index or as the error indicator by the functions that return a view index.

[edit] Example

Run this code
#include <string_view>
 
constexpr bool
contains(std::string_view const what, std::string_view const where) noexcept
{
 return std::string_view::npos != where.find(what);
}
 
int main()
{
 using namespace std::literals;
 
 static_assert(contains("water", "in a bottle of water"));
 static_assert(!contains("wine", "in a bottle of champagne"));
 static_assert(""sv.npos == "haystack"sv.find("needle"));
}

[edit] See also

constexpr size_type npos [static] the special value size_type(-1), its exact meaning depends on the context[edit]
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