24 Strings library [strings]

24.4 String view classes [string.view]

24.4.2 Class template basic_­string_­view [string.view.template]

24.4.2.7 Searching [string.view.find]

This subclause specifies the basic_­string_­view member functions named find, rfind, find_­first_­of, find_­last_­of, find_­first_­not_­of, and find_­last_­not_­of.
Member functions in this subclause have complexity at worst, although implementations should do better.
Each member function of the form
constexpr return-type F(const charT* s, size_type pos);
is equivalent to return F(basic_­string_­view(s), pos);
Each member function of the form
constexpr return-type F(const charT* s, size_type pos, size_type n);
is equivalent to return F(basic_­string_­view(s, n), pos);
Each member function of the form
constexpr return-type F(charT c, size_type pos);
is equivalent to return F(basic_­string_­view(&c, 1), pos);
constexpr size_type find(basic_string_view str, size_type pos = 0) const noexcept;
Let xpos be the lowest position, if possible, such that the following conditions hold:
  • pos <= xpos
  • xpos + str.size() <= size()
  • traits​::​eq(at(xpos + I), str.at(I)) for all elements I of the string referenced by str.
Effects: Determines xpos.
Returns: xpos if the function can determine such a value for xpos.
Otherwise, returns npos.
constexpr size_type rfind(basic_string_view str, size_type pos = npos) const noexcept;
Let xpos be the highest position, if possible, such that the following conditions hold:
  • xpos <= pos
  • xpos + str.size() <= size()
  • traits​::​eq(at(xpos + I), str.at(I)) for all elements I of the string referenced by str.
Effects: Determines xpos.
Returns: xpos if the function can determine such a value for xpos.
Otherwise, returns npos.
constexpr size_type find_first_of(basic_string_view str, size_type pos = 0) const noexcept;
Let xpos be the lowest position, if possible, such that the following conditions hold:
  • pos <= xpos
  • xpos < size()
  • traits​::​eq(at(xpos), str.at(I)) for some element I of the string referenced by str.
Effects: Determines xpos.
Returns: xpos if the function can determine such a value for xpos.
Otherwise, returns npos.
constexpr size_type find_last_of(basic_string_view str, size_type pos = npos) const noexcept;
Let xpos be the highest position, if possible, such that the following conditions hold:
  • xpos <= pos
  • xpos < size()
  • traits​::​eq(at(xpos), str.at(I)) for some element I of the string referenced by str.
Effects: Determines xpos.
Returns: xpos if the function can determine such a value for xpos.
Otherwise, returns npos.
constexpr size_type find_first_not_of(basic_string_view str, size_type pos = 0) const noexcept;
Let xpos be the lowest position, if possible, such that the following conditions hold:
  • pos <= xpos
  • xpos < size()
  • traits​::​eq(at(xpos), str.at(I)) for no element I of the string referenced by str.
Effects: Determines xpos.
Returns: xpos if the function can determine such a value for xpos.
Otherwise, returns npos.
constexpr size_type find_last_not_of(basic_string_view str, size_type pos = npos) const noexcept;
Let xpos be the highest position, if possible, such that the following conditions hold:
  • xpos <= pos
  • xpos < size()
  • traits​::​eq(at(xpos), str.at(I)) for no element I of the string referenced by str.
Effects: Determines xpos.
Returns: xpos if the function can determine such a value for xpos.
Otherwise, returns npos.